It's not always funny in Philadelphia. International headliner Jim Gaffigan served as the Pope's warm-up comic on the pontiff's recent trip to Philly, and might not have had a holy experience. Gaffigan, a comic known for his clean, family-friendly routines and his devout Catholicism, pushed buttons with a topical joke referencing the notorious 1968 Eagles game at which fans booed Santa Claus at a halftime Christmas celebration. The city is still embarrassed 47 years later, and when Gaffigan brings it up, the crowd goes silent and lets out some boos. 

Sources: CBS Philly