1. Lots of laughing.
2. NO, FREAKING, RECITING. When Monty Python's Life of Brian played in Portland in 2004 (following the success of The Passion of the Christ; well-played, that), Portland DJ Daria was at a screening where people recited. She yelled about this afterwards: "This isn't Rocky Horror, biatches!"
3. At the film's end, which almost comes out of nowhere and still feels unexpected even if you've seen the movie before, there's what feels like endless music playing over a black screen. The sheer length of that piece made people start to laugh, as it repeated and repeated and repeated again. Near the end, people (including me) were stamping along with their feet and applauding. With their hands. Do I have to spell out everything?
Now I need to see...not necessarily Monty Python's the Meaning of Life, because (honestly) I don't like the film nearly as much; it strains more for the laughs and sometimes is offensive just for the sake of being offensive, and Monty Python was better than that. BUT...I do, do, DO want, nay almost need, to see Terry Gilliam's insane short film "The Crimson Permanent Assurance" on a big screen sometime.
Oh, another bonus: before Holy Grail, the Laurelhurst showed a nine-minute bonus clip of some of the animation cut from the film, with Terry Gilliam commenting in smartassed fashion, as he's good at.