Bulbasaur

Evolve (Whenever a creature enters the
battlefield under your control, if that creature
has greater power or toughness than this
creature, put a +1/+1 counter on this creature.)
At the beginning of your upkeep, if Bulbasaur's
power is 4 or greater, you may sacrifice it. If you
do, search your library for a card named
Venusaur and put it in your hand. Then shuffle
your library.