How do you tell a 90-minute mess in just 90 minutes? Jason Reitman’s Saturday Night tells the tale of SNL’s infamous debut tape night, when it was still a giant question mark in the programming lineup, only to be a game-time decision by executive David Tebet. The evening was filled with mythology, inhabited by personalities that are just as mythological — Gilda Radner, John Belushi, Jim Henson, and Andy Kaufman, just to name a few (these four in particular are treated with a welcomed level of reverence in this film over most of the others being depicted).