Look at all these reviewers repeating themselves commenting on how your "animation has improved", "the movement" and "the voices were great"... YES WE GET IT, redundant reviews aside, YOU GUYS ARE COMPLETELY MISSING THE POINT OF THE JOKE, HOLY SHIT.
The setup is TENNIS. Red brags he's all set and even got himself a "racket"-- BUT IT'S THE WRONG RACKET. LOOK FUCKING CLOSER, RED'S GOT A "BADMINTON" RACKET INSTEAD! That's why he's exhausted and his arm fell off.
The mere fact that Red's friend doesn't even address that racket, and they non-chalantly brush it off as if it's normal is what makes this hilarious. It's the subtlety in the joke.