Jerry is fed up with Kramer’s coming into his apartment any time he feels like it and asks him to return his spare set of keys. Kramer begrudgingly complies but then lets it be known that he’s leaving for California. As for the others, the one key swap leads to multiple exchanges on pretty well everyone’s part. When Jerry forgets his keys, he gets George to let him into Elaine’s apartment so he can get his spare set. What they find interests them.