Technically, this is two episodes, but you really have to watch both of them to get the full story. With TGS on the brink of cancellation, the team pulls out all the stops and gets Tracy — who is now an Oscar winner — back for the 100th episode. The episode is packed with throwback moments and A-list cameos, including Michael Keaton as a janitor and Tom Hanks as himself. After there's a gas leak, everyone starts having hallucinations and losing their minds: Tracy and Kenneth go to the roof with a hare-brained plan and a gun, Jenna plots how to have a baby because it would be a great PR move, and Jack runs into a past, future, and alternate-universe version of himself. Watching it will make you feel like you too inhaled some gas, but in the best, most entertaining way.