The shortlived teen dramedy about kids living in 1980 had plenty of "before they were famous" actors like James Franco, Seth Rogen, and Jason Segal. We remember the main characters pretty well, but if you do a little binge watching, you'll notice that there were a ton of other cameos we've already forgotten about, including Leslie Mann, Jason Schwartzman, Rashida Jones, a many more. Apatow is basically a sorcerer when it comes to launching people's careers. But he also has a rich history of securing cameos from well-established actors. In his other shortlived sitcom, Undeclared, both Will Ferrell and Adam Sandler made guest appearances. Keep in mind that Undeclared was Apatow's follow-up project to Freaks and Geeks (which was overall better), so we can assume that Sandler - who is a friend of Apatow - would have made an appearance on Freaks and Geeks if the show had continued. He may have even been planned to play himself like he did in Undeclared. This would have been awesome for plenty of reasons. Sure, he would have been a funny addition to the Freaks and Geeks world, but it would have been crazy to see the future stars of Funny People (Seth Rogen, Leslie Mann, and Adam Sandler) appear on the same show.