Season 3, Episode 23: "The Keys"

He gave me his spare keys...

...and now he wants my keys, so I need mine back from you.

Because you have his keys? Why does he need yours?

I don't know, he said he wants to be my key brother.

-That's ridiculous. -That's Kramer.

I'll give you back your spare keys, but now I want mine back.

-Because I'll give them to Jerry. -Jerry? Why?

-Because he gave me his. -So what?