The Naked Brothers Band and another band, the L.A. Surfers find themselves competing in a "Band vs. Band" charity event benefiting Little Kids Rock, a nonprofit organization that provides free instruments and lessons to kids in low-income public schools. Rosalina starts to fall for the L.A. Surfers lead singer, Bobby Love. Nat and Alex learn his false intentions while in the bathroom (Nat and Alex hid in a stall). It annoys Nat that Rosalina likes the opponent lead singer. It turns out that Bobby is just hitting on Rosalina to get to the Naked Brothers Band, and is lying about everything (his British accent, his fear of balloons, not writing his own songs, and his name; Robert). Nat and Bobby fight, and declare at a press conference that the charity event is now a competition, and the losing band's proceeds from their next CD goes to the charity.
Cooper and the band apologize for the previous night at a later Press Conference. Cooper asks the representative of Little Kids Rock, Patty Scoggins if a "huge band in Old Europe" called "The Hunny Bunnies" (actually Mr. Wolff and Betty), could be the opening act for the event. She says that she could see what she could do.
Later Nat fails to get Rosalina to believe the truth about Bobby, he and the band make fun of Bobby and her liking Bobby, and she quits. She tells Bobby what happens (what the band thought about him). Bobby notices Rosalina's music from the Naked Brothers band, and throws it in the garbage, and after Rosalina leaves, Bobby steals it.
At the concert, Bobby attacks Nat, only for Alex to defeat him with a mere balloon that a little girl gave to him, even though it was meant for Bobby, but then she gave it to Alex and says "I hope your band kicks Bobby's band's butts!". Soon after, Bobby's band plays Nat's new song he stole from Rosalina (known as L.A. from the Naked Brothers Band) and she realizes Bobby is fake, and she runs over to the Naked Brothers, hugs Nat and she apologizes to Nat, crying. There is a net of balloons above the stage, and Rosalina wishes that all of the balloons were made of cement and they would all on Bobby Love's big fat phony head. Then, Alex reminds Nat that he's afraid of balloons. Rosalina pulls the rope, releasing the balloons. Balloons fall all over of Bobby's band, which causes him to panic and constantly yell in fear and in a non british accent for his mom, and jumps on Porky screaming, "I'M NOT PLAYING GAMES! THEY'RE TOUCHING MY FACE!" Cooper and Patty show the Naked Brothers Band music video "L.A.". Seeing this the audience and the media realizes he's a fake and the Surfers lose because Bobby stole the lyrics to the song. The Naked Brothers play Nat's new song, "Girl of my Dreams," dedicated to Rosalina and win the Battle of the Bands.