In the movie Silverado--a western, not a comedy--John Cleese plays a sheriff and his very first line is "What's all this then?"  I nearly fell out of my seat because it took me by surprise.  I didn't know JC was in the movie and just the reference to Monty Python had me laughing in the theater.  Everyone else in the theater was probably wondering what was so funny.  

My friend and I had a similar reaction when we saw Coming To America in the theater during the scene where Eddie Murphy gives the two homeless guys a ton of money and the one says "Mortimer!  We're back in business!"  If you hadn't seen Trading Places you would have NEVER gotten the reference (and we could tell several hadn't just by the looks we got when we were laughing).

Loved Trading Places.  I've seen bits of Coming To America.  I can't recall if I saw the part you're talking about.  I  probably would have remembered if I did. 
 
 
"Merry New Jear!" 

 Python always gets me laughing. Some of Mr. Beans stuff is funny to me. The Pink Panther scene regarding the dog is one of my favorites. I always thought the Pink Panther balloon scene was funny too. In one of the more recent Pink Panther movies there is a scene where the inspector goes into a sound studio and ends up in a recording space. He decides this is a good place to get rid of a little extra ballast. What he doesn't know is that he is miked up live. Some of those others I'm less familiar with. Looks like I have some things to check out.
 
 FWIW I checked out that new scifi. If you ever get queasy flying then you don't want to watch this in 3D IMAX. The special effects in this movie are incredible. The sound in that theatre was also some of the best I have ever heard. The tracks would go from something so loud that it borders your hearing threshold and then the sound drops to nothing. The mix on this movie is also incredible. If you see it I highly recommend trying to see it in IMAX if you have it in your area.

 
 The plot was a little over the edge on the believibility scale. I don't want to ruin it so That's all I'll say.

The, it's not my dog, line is one of the best!
 
It sort of reminds me of the line in Dirty Rotten Scoundrels when Steve Martin asks Michael Caine if he can go to the restroom.

James Woods' character's response in "Contact" when the Feds are discussing the significance of the first contact being a re-broadcast of Hitler's speech at the opening of the Berlin Olympics:
 
Rachel Constantine: [about Adolf Hitler] Twenty million people died defeating that son of a ****, and he's our first ambassador to outer space?
Ellie Arroway: Actually the Hitler broadcast from the...
David Drumlin: [interrupting] '36 Olympics was the first television transmission of any power that went in to space. That they recorded it, and sent it back, is simply a way of saying "hello, we heard you.
"Michael Kitz: Or, "Sieg Heil, you're our kind of people."

Did you say that booth was soundproof?
 
http://youtu.be/CvwbA5xYsk4

The Australian movie "The Castle" has many good lines. I like the exasperated lawyer, Denis Denuto, arguing with his photocopier:"I'm PRESSING f___king F1!". Really sums up photocopiers nicely. http://www.youtube.com/watch?v=KnN7U9Q8pvQ

That reminds me of one from Office Space.  While talking with some outside consultants the main character has this conversation:
 
Bob Porter: Looks like you've been missing a lot of work lately.
Peter Gibbons: I wouldn't say I've been *missing* it, Bob.
 
Love it!

Well My favorite is "Where is my dress?" ..This is my favorite....Check out