While investigating Ben's apartment, a poster for the fictional movie "Sex Panther" can be seen hanging on the wall. Sex Panther was the name of the cologne worn by Paul Rudd's character in the movie Anchorman (2004).
Reference to All That Jazz, Bob Fosse's autobiographical 1979 movie about a stressed out choreographer, director who has a heart attack. As Joe Gideon is dying he imagines an elaborate musical number with friends and family. Similarly while recovering from his health scare, Oliver imagines Charles, Mabel and his son doing a Fosse-like dance telling him take care of himself.
As Mabel and Charles are going through Gregg's apartment there's a poster of a fictional movie called "Ant Family Adventures" starring Ben Glenroy (Paul Rudd's character) as "Papa Ant". Paul Rudd in real life is the star of the MCU series of movies where he plays "Ant-man".
Noma Dumezweni, who played the critic, is best known for playing Hermione Granger in the London West End production of Harry Potter and the Cursed Child, and Ruth Younger in A Raisin in the Sun on Broadway in NYC