Super Bowl is misspelled in the title of the episode, the NFL's trademark is two words.
After Joey gets splashed with water the first time and he turns around to get a towel, actress Jennifer Aniston breaks character and starts to laugh at him. She covers her face with her hand before she recovers.
At the library when Phoebe first pulls out her guitar and the children make 'ooo' sounds, Phoebe is heard saying: "I know." But Lisa Kudrow's mouth doesn't move.
"Erica" sent a fan letter to Joey's soap opera character Drake but sent it directly to Joey's apartment, and she later showed up at his door. She could not have found his address and apartment number without knowing Joey's real name, and she clearly believed he was really Drake and had no idea he was an actor named Joey.
If Joey was being stalked by Erika then he likely could have filed a restraining order against her.
When Phoebe first meets Rob, he says "I know NOTHING about music" but at the end of the episode he's playing guitar with Phoebe while she teaches him 'Smelly Cat'.