Oliver Putnam (Martin Short) says to Charles Savage (Steve Martin), "Must you poop on every party, Charles?" In Father of the Bride Franck Eggelhoffer, played by Short, sings the song, "Party Pooper" to George Banks, played by Martin.
Selena Gomez (Mabel Mora) and Paul Rudd (Ben Glenroy) previously worked together on the Netflix movie, The Fundamentals of Caring (2016). They played Dot and Ben Benjamin respectively.
Oliver's welcome to the suspects is "Welcome, my friends, to the show that's about to end". It's a spoof of the famous verse from "Karn Evil 9 - 1st Impression" "Welcome back, my friends, to the show that never ends", by Emerson Lake & Palmer.
This isn't the first time Paul Rudd has played a character called Ben. In the movie, The Fundamentals of Caring (2016), he played the character of Ben Benjamin.