There was this mollusk and he walks up to a sea cucumber. Normally they don't talk, sea cucumbers, but in a joke, everyone talks. So, the sea mollusk says to the cucumber...
12 seconds sound clip from the Finding Nemo movie soundboard.
You can hear this line at 00:22:24 in the Blu-ray version of the movie.
Quote context
[...]
- Me? I don't... I don't have a problem.
- Oh? Okay. Denial. Just start with your name.
- Okay. Uh, Hello. My name is Marlin. I'm a clownfish.
- Well, I actually do know one that's pretty good.
- Daddy!
- For a clownfish he's not that funny.
- No, no, no, he's my son. He was taken by these divers.
[...]