Squidward Tennisballs was a name Squidward Tentacles was called on the episode "The Great Snail Race" by the mailman

where delivery man call squidward tentacle SquidwardTennisballs

Delivery Man: Package, sir.

Squidward: A-ha! (Squidward signs a clipboard) I can’t believe it’s finally here! (delivery man hands him the cage)

Delivery Man: Here ya go!

Squidward: Oh, thank you, thank you, thank you. (hands him the clipboard)

Delivery Man: Thank you, Mr...Tennis Balls.

Squidward: That’s Tentacles! (slams the door shut)

SpongeBob: Squidward’s last name is Tentacles?

Patrick: Poor guy.