I got it, but they're wrong; that version doesn't even rhyme. It's supposed to be: Jingle bells, Batman smells, Robin is a jerk. Broke the wheel on his Batmobile and now it doesn't work.
The beagle must be from House Slytherin, since he felt compelled to destroy that notorious piece of Potter propaganda, Harry Potter and the Sorcerer's Stone.
Jingle bells, Batman smells,
Robin is a jerk.
Broke the wheel on his Batmobile
and now it doesn't work.