Crabs

From Pixar Wiki

Performer:
Appeared in:	Finding Nemo

Several crabs appear in Finding Nemo. Notably, two crabs surround the sewage pipes, fighting for the scraps which emerge through the bubbles. One, voiced by Rove McManus, tries to catch Nemo, but fails.

Later, Nemo and Dory return, asking the crabs if they've seen Marlin. The crab admits that he did, but refuses to give out any information -- until Dory holds him above water, as a tempting morsel for the seagulls.