Tonight’s guest, a former SNL writer returning for another round as guest host, is John Mulaney, who had a great time, and presided over a strong show, when he first guest hosted last April. He’s heavily involved with the writers’ room, unlike many guest hosts, and the regular SNL players seem determined to bring their ‘A’ game. Speaking of ‘A’ games: In the current Co-Op episode of the IFC spoof series Documentary Now!, Mulaney parodies the perfectionist Stephen Sondheim in a program brilliantly poking fun at the documentary about the cast recording of Sondheim’s musical Company. The musical guest – of SNL, not Company or Co-Op – is Thomas Rhett.