Dean: Hey Cas you know what sucks?

Cas: Vacuums

Dean: Do you know what sucks in the metaphorical sense?

Cas: Black Holes?

Dean: Do you know what just isn't cool?

Cas: Lava?

Dean: Nevermind.

***** different conversation *******

Dean: Hey Cas I have a joke for you okay?

Cas: Sure Dean.

Dean: What mouse walks on two legs?

Cas: I don't know Dean, what mouse?

Dean: Mickey Mouse

Cas: Oh

Dean: What duck walks on two legs?

Cas: Daffy Duck? Daisy Duck?

Dean: Nope! All Ducks!!

Cas: Oh

Dean: Wasn't that funny??

Cas: I don't understand what was so funny about that joke.