Mills ended the third-quarter flurry by adding a 6-yard touchdown pass to Michael Robinson. The senior finished his final game in a Penn State uniform with 105 yards passing and led the Lions with 74 yards rushing.
Mills' touchdown pass gave him 41 for his career, tying him for the school record with Todd Blackledge and Tony Sacca. Mills will leave Happy Valley holding 18 Penn State records.
The stunned Spartans suddenly found themselves down 31-6, and any hopes of a comeback and a bowl-game bid were out the window just as quickly.
"They came out in the second half and played smarter, harder and better than we did," Michigan State coach John L. Smith said. "We didn't get the job done."
Though the Lions defense had been stingy all season, it still had difficulty coming up with that one big play that could change the momentum of a game -- until Saturday.
It started with the Spartans driving to add to a 3-0 lead in the second quarter when cornerback Anwar Phillips intercepted Drew Stanton in the end zone, a play from which the Spartans offense was never able to recover.
Calvin Lowry joined the fun with two interceptions of his own, as Penn State intercepted Michigan State quarterbacks five times.
Donnie Johnson blocked his second punt of the season, Robbie Gould closed out his career with three field goals on the day, including a season-long 47-yarder in the second quarter, and the Lions head into the offseason with some confidence.
"We felt the whole year, if we can just get one win, we might not lose for two years," Penn State quarterbacks coach Jay Paterno said. "And [last week's win over Indiana] might be -- 20 years from now we might look at it, and that goal-line stand might be the most important four plays in the history of Penn State football, who knows. And we're gonna try and make it that way."