Ever since powerhouse Penn State joined the Big Ten in 1993 they have been butting heads with the existing powers in the conference. After never playing before they were conference-mates, Michigan welcomed Penn State the conference in that first season - by ruining an undefeated season with a legendary 4 play goal line stand. It's been a heated rivalry ever since.
In recent years teams have taken turns throwing haymakers at each other and winning games by big margins only to have the favor returned the following year. One thing is certain when Penn State and Michigan take the field: it will be entertaining.