William Donohue of the Catholic League lambasted the film, and publicly protested against it for months, without actually seeing it. When his office called View Askew and requested a special screening so he could "speak about it intelligently," Kevin Smith responded "So what has he been doing the past six months?"
When Kevin Smith and Scott Mosier heard Alan Rickman was a Chasing Amy (1997) fan, they asked him to play Metatron. He read the script and came back with two questions, "Would they stay faithful to the script," and "Were the wings real or CGI?"
Jason Mewes had the entire script memorized before rehearsals. When asked why, he said it was because he didn't want to anger Alan Rickman, and because Kevin Smith took him aside before rehearsals began and said he needed to be on his best behavior and bring his A game to the set.
According to Kevin Smith, Alan Rickman held on to the maracas all day when they shot the scene in the Mexican restaurant when Metatron shook them after his meeting with Bethany. He started driving the crew and cast crazy playing with them the whole day.
(at around 28 mins) When Ben Affleck and Matt Damon are in the gun shop, you can see Ben pick up a knife and play with it. If you continue to watch Ben, you will see him cut his finger. He then recoils with a look of shock on his face. This is joked about in the DVD commentary too.
Bob Schreck, Joe Nozemack, Jim Mahfood: all as church parishioners. They all worked with Kevin Smith in comics, with Mahfood illustrating the Clerks comics, Schreck as editor on Kevin's Green Arrow run, and Schreck and Nozemack as co-publishers of his Clerks and Jay and Silent Bob Comics at Oni Press.
Kevin Smith: [Star Wars] (at around 32 mins) After meeting with Bethany, Jay says "It's like I'm Han, you're Chewie, she's Ben Kenobi and we're in that fucked-up bar!" The scene transitions are done in the same way as the Star Wars movies, wiping instead of just cutting to the next scene.
Kevin Smith: [comic books] One of the Stygian triplets wears a Hellboy t-shirt. Bartleby says, "You wouldn't like me when I'm angry.", in reference to The Incredible Hulk. Madman toys appear in the toy store.