I have a feeling I am missing a thing or two, but here it goes:
UFO crop circle
UFOs abucting beer from some more beer and pizza
Giant Squid tearing apart a boat
Note: there are a lot of squids in alot of levels-this is just one of the 5 or so. You seen one squid, you've seen em all. You can also kill the squid (I think)
Some jackdaniels whiskey in f4u
Hip flask in p38
Vodka in la7
Hidden messege in b26- "superfly is yo daddy and you know this...MAN!!!!
I kinda had to see through the plane to do this, but it is the superfly signature.
Superfly signature on the ju87
Supefly signature in AR234
Well thats it...I think I am missing one...if you have any others, post here.