I found another Squirrel eye reference

Whenever a player casts a spell, that player creates X 1/1 green Squirrel creature tokens, where X is the number of cards in all graveyards with the same name as that spell.

: Add . : Regenerate target Insect, Rat, Spider, or Squirrel. (The next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

This creature gets +1/+1 for each other creature on the battlefield named Relentless Rats. A deck can have any number of cards named Relentless Rats.