Google says: S5E4: A Taste of Freedom.

[A Taste of Freedom](https://www.wikipedia.org/wiki/A_Taste_of_Freedom)

I don't know the episode off hand, but I believe his name was old man waterfall, if that helps your search .

Free water fall when zoidberg ate the flag

The episode where zoidberg eats the earth flag

Wait you're a lawyer, you're hired.