Clone

A clone character is a common inclusion in the Super Smash Bros. series, and many other fighting games as well. It describes two or more characters that have nearly identical movesets with slight variations in the attack properties and/or character stats. From the developer's perspective, a given character's model can be used as a base template from which to build another, and it is usually evident which one is the "original" and which is the clone. Most clones are from the same series of games, with Ganondorf being the only clone of a character who is not in his franchise.

There is a difference between Clone characters and Semi-Clones, but for the purposes of this article, we’re going to refer them as the same. Like Mario and Luigi vs Pit and Dark Pit.

Also as of Super Smash Bros Ultimate, Clone characters are now referred to as “Echo Fighters”, With Dark Pit, Lucina, and the brand new addition of Daisy, being echoes of Pit, Marth, and Peach. (Dr. Mario is in fact not an Echo Fighter).

Semi-clones
Semi-cloning (sometimes referred by fans as "Luigification") is when a character has some attacks that are similar to those of another character, while still having some variation in terms of moveset or special attacks. The term originated from Luigi, who was originally nearly indistinguishable from Mario, but has slowly been given his own unique characteristics and attacks. This is similar to the development of Luigi throughout the Mario series' development.

Many clones from Melee were then given semi-clone qualities before they returned in Brawl, while some did not return. The exact meaning can vary for different people. Some believe that any character with clone-like traits that has any variation in attacks are semi-clones, while others think that certain characters need more unique attacks to be a semi-clone.

Mario & Luigi

 * Luigi has a different Dash Attack, a different Down Tilt, and his Super Jump Punch's beginning is a strong move, although they are visually identical. His fireballs are not affected by gravity, and his Down Special launches the foes instead of sucking them in, despite also looking the same as Mario.

Non-playable

 * The Fighting Polygon Team is composed of clones of all the playable fighters.
 * Metal Mario is an exact copy of Mario, but with more weight and flinch resistance.
 * Giant DK is a copy of normal DK, but is much larger.

Clones in Super Smash Bros. Melee
In each pair, the former is the "original", while the latter is the clone. Direct clones are usually identified in Melee by having a slightly recessed character selection box next to the original character's.

Mario & Dr. Mario

 * All attacks are similar, but have "Doctor" variants. Dr. Mario's Forward Smash has electrical properties. Dr. Mario's F-Air is not a weak Meteor Smash like Mario's, but is a very powerful aerial attack with vertical knockback. Interestingly, none of Dr. Mario's moves make the "smacking" sound that some of Mario's moves have. In terms of attributes, in comparison to Mario, Dr. Mario had traded some of his speed for attack.

Fox & Falco

 * Almost all attacks are similar, although their special moves have slightly different properties, and Falco's D-air is a single hit Spike. Falco's SSBM properties resemble Fox's original SSB properties.

Pikachu & Pichu

 * They both have a few unique animations in walking/running and one unique attack for their Up Smash. Pichu hurts itself when using electric and special attacks.

Captain Falcon & Ganondorf

 * Different Forward aerial, some different effects, Down Smash functions differently; the first hit is necessary for the second hit to land, granted the opponent is in front of Ganondorf. Ganondorf doesn't have an A Combo, instead his regular A move is stronger.

Note: They are the only pair of "original and clone" to originate from different universes.

Link & Young Link

 * All attacks are similar, except for Young Link's Standard Special Move, where he shoots flaming arrows. Also, when Young Link attacks, his sword does not make a "slashing" sound, but it instead makes a "slapping" sound. However, his Up Throw involves his sword, and it makes a slashing sound only then. Down aerial is a Spike, provided Young Link lands the attack with the hilt of his sword.

Marth & Roy

 * All attacks are similar, with the exception of Roy's Up Special Move and Roy's sweetspotted Up Smash, which spikes. Also, while Marth's are most powerful at the tip of his blade, Roy's are stronger the closer the foe is to the center of his blade. The "sourspot" of Roy's sword attacks make a "slapping" sound instead of a "slashing" sound.

Note: They are also the only pair of "original and clone" to both be hidden characters. Roy's similarities to Marth have been said to have been the reason that Roy was replaced with Ike in Brawl.

Non-playable

 * Bowser & Giga Bowser
 * Captain Falcon-Ganondorf/Princess Zelda & Male/Female Wire Frames
 * Master Hand & Crazy Hand

Mario & Luigi

 * The former clones were differentiated with separate normal movesets and side specials. Luigi has a different Side Special than Mario (Luigi has Green Missile, Mario has Cape). They have different Forward and, to a lesser extent, Down Aerial attacks. They also have a different Forward Smash Attack, different Up Tilt and different neutral combo.

Luigi & Dr. Mario

 * Since Dr. Mario is a clone of Mario, they have similar properties. Dr. Mario had also pinched Luigi's down special.

Clones in Super Smash Bros. Brawl
Most clones have since been "Luigified" in Brawl, and while some agree that clones are entirely non-existent in this game, debate continues over whether or not Toon Link is a clone of Link, despite sharing a vast majority of the latter's moves. But for the majority of fans, Brawl features only semi-clones.

Link & Toon Link

 * Although most people consider them to be clones, there are notable differences. The differing moves are Up Smash (which shares the first strike), Neutral Aerial, Forward Aerial, Back Aerial, Forward Throw, and Back Throw. Also, Toon Link's Down Aerial is a Stall-Then-Fall Aerial and a Meteor Smash, but still shares the same animation, along both Spin Attacks and Side Smashes. Toon Link's moves have slightly different properties but ultimately share poses and animations, making him the closest clone the game has.

Fox & Falco

 * Reflector works differently, and Blaster is slower but more powerful. Non-cloned moves include neutral combo (in addition to a different animation, Fox's will repeat the first punch as long as the button is held, while Falco will not), U-Tilt, N-Air, F-Air and Forward Smash. Falco's Back aerial is now a sex kick. Also, they share a similar Final Smash (Falco's Landmaster hovers higher with superior air mobility, while Fox's Landmaster has stronger blasts). While their Up Aerials are similar in animation, Falco's is performed on a slightly different axis.

Captain Falcon & Ganondorf

 * A completely different Final Smash and some different standard attacks (neutral, all tilts, Up Smash and F-Air), but some normal moves are still similar. And most notably, they both share 3 special moves, with the main cosmetic difference being that Captain Falcon has fire effects in his specials, while Ganondorf's specials feature darkness or electricity. Raptor Boost and Flame Choke are initially similar, but the difference is that Raptor Boost launches the opponents, while Flame Choke grabs them, slamming them straight down.

Ness & Lucas

 * Share three special attacks that have some differences. Ness has PK Flash & Lucas has PK Freeze. However, PK Freeze & PK Flash still work a little similarly, despite moving and looking differently with completely different hitboxes. Both characters' PK Fire are almost entirely different, with the only similar traits being the name and the fire element. Their Final Smashes also have similar animations and the same name, however, Ness' produces vertical knockback, while Lucas' produces horizontal knockback. A few of their standard attacks have similar animations, such as Forward Smash, Up Aerial, and Down Tilt.

Mario & Luigi*

 * The differing moves are neutral combo, Dash Attack, Up Tilt, Down Tilt, Forward Smash, Forward Air and Down Air. Two of their specials are different (while their Super Jump Punches have unique properties, they still have similar animations), as well as different Final Smashes.

Note: Now that they barely share any moves, many smashers don't even consider them to be semi-clones at this point.

Fox & Wolf*
[ *] There has been much debate over whether or not these pairs of characters are semi-clones.
 * The only moves that are almost identical are their Final Smashes and Down Special moves. Side and Up Specials are similar in function, but differ in damage, hitboxes, and animations. Blasters are also different, as Wolf's has a direct attack hitbox in the form of the blade attached to his gun that actually has knockback with potential to KO. Almost all of Wolf's standard attacks are different from Fox's.

Non-playable

 * Captain Falcon & Red Alloy
 * Princess Zelda & Blue Alloy
 * Mario & Yellow Alloy
 * Kirby & Green Alloy

Clones in Super Smash Bros. for Wii U and Nintendo 3DS
In Wii U/3DS, there are only three characters that are complete clones: being Lucina, Dark Pit and Dr. Mario. The other characters that were already semi-clones are now further more distinct, with many tweaked animations.

Marth, Roy and Lucina

 * Lucina is a complete clone of Marth, sharing nearly all animations with him; however, their only notable difference is that Lucina's power is not concentrated on any point of the sword, being the same damage in all the range of the move, while Marth's is concentrated in the tip. Her blade is also slightly shorter than Marth 's.
 * Roy is now a more of semi-clone, and while he has similar attacks as both Marth and Lucina, his moveset became unique with his own animations, while retaining some similarities from Marth's animations, and having similarities in some moves.

Link and Toon Link

 * Link and Toon Link retain almost all of their similarities and differences from Brawl. The only differing moves are Up Smash (which shares the first strike), Neutral Aerial, Forward Aerial, Back Aerial, Forward Throw, and Back Throw. Also, Toon Link's Down Aerial is a Stall-Then-Fall Aerial and a Meteor Smash, but still shares the same animation, along both Spin Attacks and Side Smashes. Toon Link's moves have slightly different properties but ultimately share poses and animations. They also have the same Final Smash; the only differences are that Link's Triforce is more powerful but Toon Link's reaches a longer range.

Mario, Dr. Mario and Luigi

 * Same attacks for the most part, with some cosmetic changes. Much like in Melee, Dr. Mario is slower and more powerful than Mario or Luigi with some attacks that have electrical properties. Dr. Mario's Doctor Finale is the same as the Mario Finale, but with no fire effects and different sound effects. Their Down Special is also different, with Dr. Tornado being similar to Luigi Cyclone.
 * Luigi retains pretty much the same properties and animations he had in Brawl with slightly tweaks to further difference him from Mario.

Pit and Dark Pit

 * They share the exact moveset with the same damage and knockback properties save for a few moves, such as Forward Tilt. Up and Down Special Moves are the same, with the Neutral and Side Specials differing slighlty. Along with aesthetics, Pit's Side Special deals vertical knockback while Dark Pit's deals diagonal knockback. Dark Pit's Neutral Special deals more damage, but has a much wide turning circle. The only move truly unique to them is their Final Smashes, though it could be argued that Dark Pit's is a clone of Zelda/Shiek's.

Mii

 * Many of the Mii's regular and special attacks resemble those of actual fighters. They copy or take inspiration from others with similar attributes, with few or many differences. Additionally, in some instances, animations and damage outputs are very similar. The copied specials are as follows;
 * Brawler copies the Ultimate Uppercut from Donkey Kong's Giant Punch, Exploding Side Kick (Capt. Falcon's Falcon Punch), Burning Drop Kick (Pikachu's Skull Bash), Soaring Axe Kick (Ike's Aether), Piston Punch (Little Mac's Rising Uppercut), Head-On Assault (Bowser's Bowser Bomb), and Feint Jump (Zero-Suit Samus' Flip Jump). The Final Smash Omega Blitz is a copy of Ike's Great Aether.
 * Sword Fighter copies the Slash Launcher from Ike's Quick Draw, Stone Scabbared (Ike's Aether), Skyward Slash Dash (Fox's Fire Fox), Hero's Spin (Toon Link's Spin Attack), Blade Counter (Marth's Counter), Reversal Slash (Mario's Cape), and Power Thrust (Capt. Falcon's Falcon Kick). The Final Smash Final Edge is a copy of Wii Fit Trainer's Wii Fit. Gale Strike mimics the Ore Club's tornado in function and Link's Gale Boomerang in design, Blurring Blade resembles a multi-hit version of Marth's Shield Breaker, and Airborne Assault seemingly blends Shiek's Bouncing Fish and Pikachu's Skull Bash.
 * Gunner copies the Charge Blast from Samus' Charge Shot, Laser Blaze (Fox's Blaster), Flame Pillar (Robin's Arc Fire), Stealth Burst (Zelda's Din's Fire), Gunner Missile (Samus' Missile), Cannon Uppercut (Palutena's custom Rocket Jump), Arm Rocket (Pit's Power of Flight), Echo Reflector (Fox's Reflector), and Absorbing Vortex (Ness' PSI Magnet). The Final Smash is a copy of Samus' Zero Laser. Bomb Drop resembles Samus' Bomb, and Laser Blaze has qualities of Falco's Blaster.

Greninja and Zoroark
Despite Zoroark being an Assist Trophy, it shares the same attack as Greninja's Final Smash, but only a little bit weaker.

Ike and Chrom
During Robin's Palutena's Guidance dialogue, Virdi mocks Chrom for being a "Carbon copy" of Ike, and Palutena states he lacks an Aether recovery move. The former statement references the same belief held by the Fire Emblem fanbase while mocking their similar character and fighting style in the franchise.

Ironically, Chrom can learn the Aether skill like Ike can after being promoted to the Great Lord class in Fire Emblem: Awakening. Unfortunately, this furthers Virdi's point.

Ryu and Ken Masters
Despite Ken being an unlocked trophy and having his theme in the game, his best friend and rival, Ryu, being one of the two first very characters in a fighting game to share a same moveset, and a very well known for foundation of "Shotoclone", Ken is a first clone character to appear in history. Except in Street Fighter II until onwards, Ken utilizes more fiery attacks like his Shoryuken (later also some variations of Tatsumaki Senpu Kyaku as of Marvel VS Capcom series and Street Fighter V), and mostly having a different super moves since the terminology was introduced in Super Street Fighter II Turbo.

Young Link & Toon Link

 * They have some similar attacks, along with their Spin Attacks being similar in both appearance and function. Toon Link is considered a spiritual successor to Young Link as the later was removed from  Brawl  to give spot to him.

Trivia

 * Data mining in Super Smash Bros. for Wii U and Nintendo 3DS suggests that Olimar and Alph were originally planned as separate characters, rather than Alph being an alternate costume. Data for a possible "Rock Pikmin" was also found.