Reading the other posts, I decided not to vote. I was thinking the same thing Justeazy was, but not exactly. It seems logical that characters can do partnered attacks, but for Ganondorf and Link I think it'd be more of a rivalry ability. For example, only Link and Toon Link can reflect Ganondorf's light orbs because the characters have the Master Sword and Link and Ganondorf are rivals. I feel like Kirby and Meta Knight would have more of a rivalry ability, since you always seem to fight Meta Knight. (That's been announced to change in the upcoming Kirby game for WiiU.) For the Kirby and Meta Knight rivalry, Kirby would gain the ability of Sword Kirby, because a sword always appears when Kirby and MK face off. The two characters in the same battle would result in the sword appearing with the familiar "Get it!" sign, however only Kirby could snag the sword. Of course, this would result in new attacks (and maybe special attacks) until Kirby either takes enough damage to lose the ability or taunts, also resulting in him losing the ability.
It's an interesting concept, and would be a great thing to include in a future version of SB.