Whenever another creature you control enters, put a +1/+1 counter on that creature.
Illustrated by Kee Lo · Jumpstart: Historic Horizons · #694
There are no rulings for Good-Fortune Unicorn.
Whenever another Ally you control enters, put a +1/+1 counter on this creature.
Alliance — Whenever another creature you control enters, put a +1/+1 counter on this creature.
Whenever a creature you control enters, if that creature is 1/1, put two +1/+1 counters on it.
Whenever this creature or another Ally you control enters, you may put a +1/+1 counter on this creature.
Whenever another green creature you control enters, put a +1/+1 counter on target creature.