Jeffrey Beanpile

Whenever a creature with power 4 or greater
enters the battlefield under your control, put a
Bean counter on Jeffrey Beanpile.
If Jeffrey Beanpile has 4 or more Bean counters,
remove all Bean counters from Jeffrey Beanpile
and create that many 1/1 green Plant creatures.
Then exile Jeffrey Beanpile and return it battlefield transformed under your control.