Two bullfrogs enjoy a few comical scenes in Chrono Trigger. They first explain how to operate the switches in Sewer Access, and later, they appear if the party opts out of the Black Omen at a Nu's request. They are a programmed enemy, though their stats are unfinished; the entry on them is at Bullfrog.
Depending on when they're used in the Black Omen, they speak unique dialogue.
[1000 AD] UNDERLING: You're starting to bug me! How long do I have to put up with your drivel, ribbit? BOSS: Just shut up and push, will ya, GRIBBIT! [600 AD] UNDERLING: Hey, Boss. What's your life's dream, ribbit? BOSS: My personal dream? To be King of the Sewer! Gribbit! [12000 BC] BOSS: Oh, all right...! What's your little dream? Gribbit. UNDERLING: I just want to keep being your apprentice, ribbit. BOSS: Sheesh! You're making me cry, here. I'm gonna tell Krawlie what you just said!!