Monsterpiece Theater

Monsterpiece Theater is a recurring Sesame Street sketch hosted by Cookie Monster as Alistair Cookie. The sketch parodies the PBS series Masterpiece Theater, originally hosted by Alistair Cooke.

This segment has had at least three different openings, the first two of which specifically reflected the then-current Masterpiece Theater opens. On one early skit, "Me, Claudius", it featured no title card and opened on the camera panning across various statues before trucking over to Alistair Cookie as the Monsterpiece Theater opening theme music was heard (composed by Sam Pottle). The first regular opening sequence had the title on a blue background, with a Union Jack flag as the P in "Monsterpiece", with the camera zooming out on the flag. Most of these skits with this opening had Alistair Cookie with a pipe and then usually eating it at the end. Around Season 21, the library that Alistair Cookie was in was changed, and the pipe was dropped. In Season 23, this opening was replaced with a longer opening, which panned around a room, showing pictures and books referencing past segments. The opening theme music was also re-recorded to sound more full and orchestral, though using the same tune, and was also presented in its entirety. The name of the skit was also spelled as "Monsterpiece Theatre" in this intro. In Season 27, another new opening was produced with the title sliding in front of a computer-animated green curtain. Whenever a new opening was added, that opening would be used in all segments shown in those episodes, even if that particular segment was made years earlier. Skits that originally had Alistair Cookie's pipe had the opening and closing footage with Cookie re-taped, often using the original 1980s voice recordings by Frank Oz.

Similar segments have appeared in recent years sharing certain elements with the "Monsterpiece Theater" segments. In Season 37, "Dinner Theatre" premiered in which food themes are used to parody classic plays and musicals. The following year in Season 38, Cookie Monster bookended a sketch he describes as an "Amercan Monster Classic." In it, Grover plays a monster who has forgotten his keys, in a take on A Streetcar Named Desire.