With 'Men in Black 3' not exactly impressing critics, it seems like Will Smith's best days may be behind him. And judging by the reaction at the 'Men in Black 3' premiere after party, it could be way behind him.

The crowd at the party went nuts when Smith took the stage with his former partner DJ Jazzy Jeff for an impromptu concert that included some classic jams.

In addition to the obvious "Men in Black" theme song, Smith and Jazzy (Mr. Jeff?) also performed their classic hit "Summertime" and, yes, the 'Fresh Prince of Bel-Air' theme song.

Given how excited fans get to see Smith rapping again, it's somewhat surprising he stepped back from the responsibilities with the 'Men in Black 3' theme song, instead letting Pitbull record "Back in Time."  Smith always seems so uptight, it's fun to see him loosen up and get back to the old days (this is, after all, the man who once wrote an entire rap about 'Nightmare on Elm Street').

You can watch some audience video of "Summertime" (still one of the all-time great summer anthems) below and if you've got a hankering to watch him perform the 'Fresh Prince' theme song, you can watch his rap on a BBC talk show here.