Ivysaur is the evolved form of Bulbasaur. In the RPG series, Bulbasaur evolves into Ivysaur at level 16, a relatively early level, and then evolves into Venusaur, who is a Poké Ball Pokémon in the Smash Bros. games, at level 32.
Ivysaur appears as a moderately large, blue, squat, quadrupedal saurian with the plant on its back now in the form of a pink bud and large green leaves. The bulb formerly on its back has grown and partially bloomed both to exposure from sunlight and apparently from drawing energy from Ivysaur's own body, which also gets stronger when it absorbs sunlight. The budding flower is heavy enough that Ivysaur appears to lose the ability to stand on its hind legs, but its four legs and trunk grow thick and strong from the weight of the flower, even as a quadruped. If it starts spending more time lying in the sunlight, it is a sign that the bud will bloom into a large flower soon, which would be heralded by the bud giving off a sweet, pleasant aroma and the species' evolution into its final form, Venusaur.
Ivysaur is briefly mentioned in both Venusaur's and Bulbasaur's trophy descriptions.
As a playable fighter
Ivysaur makes its debut in the Super Smash Bros. series in its third installment, Super Smash Bros. Brawl. It is playable as one of the three Pokémon used through Pokémon Trainer, the other two being Squirtle and Charizard. It is the middleweight of the trio of Pokémon that Pokémon Trainer can use, and it is equipped with a tether recovery up special attack.
Ivysaur, along with Squirtle, did not return as playable characters in Super Smash Bros. 4. However, it does appear in both versions of Super Smash Bros. 4 as a trophy.