biggest frog in the puddle

and biggest toad in the puddle

Prov. The most important or powerful person in some small, unimportant group. Jill: Elaine seems to be obsessed with becoming class president. Jane: Yes, she really wants to be the biggest frog in the puddle. The people in my office don't care about doing their work; mostly they compete over who will be the biggest toad in the puddle.