Know some people who know some people.
Those people happen to be Scientologists. And Will, like Travolta, has been mixed up in their bullshit for a minute.
Ain't no hard evidence here, but it adds up. Will needs a beard. Jada (was) a good 'un. Until she wanted to get some real dick that was into her. She splits. Will panics because if you want to be an A-lister who appeals to the majority of Americans you gotta keep up appearances a la Tom Cruise. So he gets her back but she's putting him through the ringer. He can't bail because then it all comes out. So Jada wears the pants in that fucked up family. And of course, he's being ridiculed for being a cuckold, etc. Can't sit well with a guy who is used to having everything go his way.
If you play the tape back, Will is laughing at Rock's joke. People think he went nuts because he saw Jada looking pissed, but they only think that because the camera cut to her reaction right before he got up. In reality, you can hear Rock say "Aw, that was a nice one." Implying he could have been making jokes about Will being a cuck. THAT'S when Will gets up, acts a fool, and then is trying to hold back tears while yelling once he gets back to his seat. He panicked. Wife who owns the keys to his life is pissed and Rock is hinting about some serious shit Will has already taken plenty of heat for. Time to flip the fuck out.
Dude is having a mental breakdown because Jada has the goods on him and he's trapped. Or maybe he just really misses his wife's hair. Who the fuck knows.
I haven't watched every episode of Fresh Prince, but I too sat through I Am Legend on a date. Decent enough flick. Ending definitely could have been better. Should have stuck more to the novel where he's actually seen as the bad guy by all the vamps.