Foul Play is a set in a Victorian looking theater. It's drawn like a cartoon and is about humor as much as it is about action.
The protagonist is Baron Dashforth, a retired daemon hunter who stars in a show about his life. In this sidescrolling game, you have to defeat the villains (/actors) coming at you in all the different acts of the play. However, you're not supposed to just beat them up, you must try to do so in the most theatrically ways to amuse the public. They take up the lower part of the screen and your action will impact their behavior.
It's possible to play this as a two player co-op game, by calling in sidekick Scampwick.
from the game site
A side-scrolling brawler that rewards performance over pummeling
Join daemon-hunter Dashforth as he recounts his incredible life-story on stage
22 Incredible Acts: From the deserts of Cairo to the DEPTHS of Atlantis
Over 50 hideous enemies drawn from the Baron's recollections
Learn 12 Electrifying stage-tricks to bring the house down
Have a friend join as sidekick Scampwick in Local & Online Co-op play
Available on XBOX Live and Steam PC
Beautifully animated scene changes re-create the Baron's adventure
Never before seen 'Daemon Diary' charts the discovery of Daemonology