Once again Ernie makes preparations for an extremely unlikely scenario.
BERT: Do I ask you to sing to my paper clips?
ERNIE (*sotto voce*): "vo vo vo de oh!"
BERT: Do I have to do that?
ERNIE: Okay Bert, that was not bad for a first time, Bert, but we need more feeling, Bert!
BERT: I like singing to your Rubber Duckie! We established a relationship!
Also, at the beginning when Bert is singing really fast and Ernie tries to pick up the squeaking cues correctly.
They skipped the bridge section, which is my favorite part. Grr. ;)