Dungeon ghouls

Whenever Dungeon ghouls come into play and
one or more players have 1/1 or 2/2 creatures
on the battlefield, a maximum of two of those
creatures get converted to
Black / Green 1/1 creature ghouls (undead)
The caster can choose which ones to convert
if there are more than two 1/1 or 2/2 creatures
on the battlefield.