Teetering is an animation that is naturally activated by standing near a ledge in all four instalments of Super Smash Bros. The character will automatically start teetering back and forth over the edge with a panicky expression (an animation that can only follow the laws of cartoon physics, in which they can not begin falling downwards until he/she stares at the ground).
The effect can only be done when a player walks towards the edge slowly. Simply landing near the edge does not count, and moving too quickly will simply cause the character to run off the edge. While teetering, a character will not walk off the edge unless the Control Stick is tilted past a certain amount; otherwise, the animation is an easter egg, and does nothing but alter the character's standing animation.
Characters will teeter regardless of whether the edge they're hanging over can be grabbed onto. Characters will stop teetering if they take any action (such as attacking).