Phineas and Ferb: the Brave and the Bold! is an upcoming crossover between Batman: the Brave and the Bold and Phineas and Ferb. It is one of many planned B:tBatB crossovers.
Batman and Captain Atom put a halt to Mitch's plans to capture endangered animals and put them in his private zoo.
Phineas and Ferb decide to team up with Batman and Green Arrow, who are in town when their mutual nemesis, the Clock King, is in Dansville. Meanwhile, Perry the Platypus must stop Doofenshmirtz's plans to outshine other supervillains by eliminating Batman, while Candance, after hearing that Batman and Green Arrow are Jermey's favorite superheroes, tries to get their autographs for him.
Isabella: Hey guys! Whatcha doin'?
Phineas: We're gonna team up with Batman and Green Arrow to track down Clock King and put a stop to his plans!
Isabella: Wait, what?
Aren't You A Little Young?
Batman: Aren't you kids a little young to be working with superheroes like us?
Phineas: Yes; yes we are.
(about the Batmobile) That's one sweet car.