May's Venusaur is the third Pokemon obtained by May. She first appeared in Grass Hysteria.
Venusaur as a Bulbasaur lived with her parent, Venusaur with the grass-type Pokemon when May discovered her. When Team Rocket came to capture all of the grass Pokemon, they grabbed Bulbasaur too and were planning on grabbing Venusaur, but Bulbasaur was saved by May and Venusaur and Team Rocket was sent blasting off.
Venusaur is kind and friendly to her trainer. She has a fondness for Ash's Bulbasaur.