Cloud's pose in his official artwork in Smash Bros. mimics his pose from his official artwork from Final Fantasy VII.
Cloud is the first character from Square-Enix to appear in the Smash Bros. series.
He is notable as Final Fantasy VII never came to any Nintendo systems, although the game was initially planned for the Nintendo 64 before moving to the Playstation.
Cloud, however, did appear in music spinoff Theatrhythm Final Fantasy and its sequel, Curtain Call, on Nintendo 3DS, as well Kingdom Hearts: Chain of Memories on Game Boy Advance.
Cloud's announcement, "Storms Into Battle!", is a joke referencing his name, as some protagonists of Final Fantasy games bear names that have relation with weather (i.e. Cloud, Squall, Tidus).
Cloud's dashing animation is a reference to the movement system of gliding seen in Dissidia Final Fantasy.
Despite being an unique character, many of his attacks appear to have borrowed animations from other characters in the game, most notably Ike, Shulk and even Little Mac.
Cloud's trailer makes various references to Final Fantasy VII itself:
The very beginning of the trailer is a nod to the opening, of the original game, showing the small glows of Lifestream flowing through the air.
At 0:51, the screen twirls and the iconic Battle Theme starts to play, referencing the random encounters present in the game. Also, Charizard, Samus and Kirby appear lined up against Cloud, a nod to the turn-based system.
At one point in the trailer, one shot shows Cloud riding King of Red Lions while looking quite dazed, referencing a discussion on motion sickness he has with a travel-sick Yuffie Kisaragi in the original game aboard the Highwind airship, although Cloud himself doesn't suffer motion sickness during the game.
At 1:06, Cloud is shown lied down in front of Zelda, in her crouching animation, holding a Lip's Stick, with some Pikmin, at the Kalos Pokémon League stage. This is a reference to his first encounter with Aerith, the flower girl, who one of the main characters in Final Fantasy VII; he meets her after falling from the Sector 5 Reactor, blasting through a church ceiling and landing on a flower bed that is cared by Aerith. The stage in question also references that very church.
At 1:25, Cloud, seen in his Advent Children alternate costume, attacks Wario in his Wario Bike, proceeding to picking it up and walking away with it. This references the motorbike minigame from the original game in which Cloud rode a motorbike and protected his friends (in a pickup truck) from a convoy of Shinra bike troopers. This is also a reference to Cloud's own bike, the Fenrir, in the animated feature Final Fantasy VII: Advent Children.
At 1:39, Cloud is seen performing his signature casting animation from Final Fantasy VII (which is one of his Taunts) near the Prince of Sable, who proceeds to transform into a frog. This is a reference to the recurring magic spell, Frog, seen in the series. In Final Fantasy VII it is accessible through the Transform Materia. As the name suggests, the magic turns enemies into frogs.
At 1:58, the trailer showcases the Midgar Stage, where various Summons appear, among them Odin, Leviathan, Ramuh, Ifrit and Bahamut ZERO.
At 2:16, Ike and Cloud are seen standing in front of each other, with close shots of their faces, while Cloud is holding a Smash Ball, and proceeding to unleash his Final Smash, Omnislash. This is a reference to the scripted battle that happens between Cloud and Sephiroth by the end of the game. This also references the fact that Omnislash resembles Great Aether in terms of functionality.
At 2:36, Cloud is seen at Gaur Plains, as six Mii Fighters are seen running and jumping around using the Chocobo hat, referencing the Chocobo Farm, a place where Cloud can breed Chocobos. A seventh Mii Fighter using the same hat, but much larger, is seen sleeping the right side, which in turn references Chubby Chocobo.