Northwestern has a bye this week, giving the Wildcats extra time to prep for Penn State on Nov. 7 ... and to fully immerse themselves into the Halloween spirit.

And boy they sure did, as coach Pat Fitzgerald and the team showed up to Friday's practice in full-on costumes to surprise the assistant coaches.

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And the team flew their freak flags high, what between Batman doing drills in full mask and cape, King Tut making his runs, or all four of the Ninja Turtles holding the line:

Props to the B1GCats team for putting this highly entertaining clip together.

In the words of one assistant coach: "I tell ya: wow."

H/t Extra Mustard.