Skullroy Jenkins is a bizarre phenomenon encounter mostly when the character Skullsmasher is in an instance.
The telltale signs of this phenomenon are usually a large green object running headlong at opponents that it clearly will not be able to defeat. Of course Skullsmasher will tell you that this is either because he's playing in character or that he didn't really know.
This event was first spotted during the opening of Ahn'Qiraj when Skullsmasher accidentally triggered the event in the smaller AQ instance that makes all those big nasty creatures run at you. Fortunately a wipe was avoided and there was much rejoicing.