Yes, there is an extra scene after the credits. It contains a callback cameo; see here or here for more details.
Similar to the Griffins' and Seth's previous two big screen movies, a longer "Extended Version" or "Unrated Version" with approx. 10 more minutes has been released on Blu-ray and DVD. As often, the new footage was not removed from the Theatrical Version for censorship reasons. Although it is obvious that most of that footage was cut for pace reasons, fans will enjoy it.
