Simon Pegg revealed on Twitter that he and Nick Frost will be reprising the roles of Shaun and Ed from Shaun of the Dead for an upcoming Phineas and Ferb Halloween Special.
According to Wikipedia, Shaun of the Dead is a 2004 zombie comedy film directed by Edgar Wrightand written by Wright and Simon Pegg, and starring Pegg and Nick Frost. Pegg plays Shaun, a man attempting to get some kind of focus in his life as he deals with his girlfriend, his mother and stepfather. At the same time, he has to cope with an apocalyptic uprising of zombies.
— Simon Pegg (@simonpegg) August 18, 2014