A couple of nights ago, Will Smith stopped by David Letterman's 'Late Show' to promote his newest film 'After Earth.' But before he did, the one-time Fresh Prince delivered an impromptu summer jam. 

While making his way to the chair, Big Willie Style noticed the CBS Orchestra was playing a familiar tune: the rapper/actor's '90s favorite 'Summertime.' Naturally, he took to the mic and made the crowd realize why parents just don't understand. Oh wait, wrong Will Smith song. Regardless, the rap obviously excited both the crowd and band alike.

So where was DJ Jazzy Jeff during the performance?