Ivy Lane Denizen

Whenever another green creature you control enters, put a +1/+1 counter on target creature.

Llanowar Elves

Forest

Priest of Titania

{T}: Add {G} for each Elf on the battlefield.

Elvish Mystic

Scurry Oak

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Whenever one or more +1/+1 counters are put on Scurry Oak, you may create a 1/1 green Squirrel creature token.