Guppies: Good morning Mr...Grumpfish?!
Mr. Grumpfish: What's so good about it.
Molly: Uh, Mr. Grumpfish? What are you doing here?
Gil: Where's Mr. Grouper?
Mr. Grumpfish: He's at the dentist. I'm your substitute.
Mr. Grumpfish: Substitute teacher.
Nonny: A substitute is a teacher that takes care of you when your regular teacher's away.