Deadpool will be featured in the upcoming episode of Ultimate Spider-Man airing 7/7/2013 called, "Ultimate Deadpool". Thanks to Kendra for the tip. [SOURCE]
Season 2, Episode 16
Spider-Man spends a day in Deadpool's madcap world.
Guest Cast Will Friedle: Deadpool
UPDATE: Former Deadpool writer Joe Kelly confirmed that he worked on the episode via twitter.