Britney Spears stepped out with Johnny Knoxville and the rest of the guys of Jackass to shoot a bit in LA today. The sketch aired during tonight's episode of Jimmy Kimmel Live, where Britney also performed her three song series in new costumes — we were in the audience so check out some pictures on our Twitter! Johnny was one of Jimmy's guests this evening and during his interview, he joked that Britney actually made a cameo in Jackass 3D that didn't make it into the movie. Jimmy then showed the spoof clip, which had Britney participating in one of their very gross port-a-potty stunts. She wasn't afraid to get a little dirty for a laugh, but was all cleaned up when she took the stage. She reprised the sexy moves she debuted in Vegas and SF over the weekend, and it's even more exciting since Femme Fatale was finally released today! Earlier this morning during her Good Morning America show Britney announced plans for a US tour this Summer with Enrique Iglesias, though, unfortunately, he already pulled out due to the high production costs of moving her elaborate sets.