The Scary Movie movies can always be counted on for some larfs, sure. This one, though, seems to just use the "throw shit at the wall and see what sticks" philosophy, cramming together parodies of Saw, War Of the Worlds, The Village, Brokeback Mountain, The Grudge, Land of the Dead, and even Million Dollar Baby gets shoehorned in. The result has all the cinematic value of a "Weird Al" video.
The jokes hit all the most-popular-search-engine-search sorts of topics: Viagra! The "Dirty Sanchez" (which everyone laughs at, whether or not they get it)! Michael Jackson! If you laugh, you're laughing out of reflex, not out of genuine comedic response. It's like laughing at Dana Carvey's "Johnny Carson" impression it no longer matters that it's not funny; you just laugh. A second tier of jokes mine territory that was obsolete even 20 years ago. A Three Stooges joke? A Nude Bomb joke?! This is some cutting-edge shit.
The cast seems to have fun. Chris Elliot collects another way-beneath-him paycheck; Leslie Nielson shows up to make you wonder what might happen if he were to try to return to drama at this point. Lil Jon makes a cameo, securing his position as the George Clinton of his generation, maintaining his presence through shoddy film cameos instead of, oh I don't know, music. Some unexpected successes: Carmen Electra shows that she actually has great comic timing; and the "Girls Next Door" girls (Holly Madison, Bridget Marquardt, and Kendra Wilkinson) demonstrate some sense of self-awareness. Cloris Leachman once again reminds people how comedy is done, and a Saw parody sequence with Shaquille O'Neal and "Dr." Phil McGraw is much funnier than it has any right to be.
But somehow, in spite of all the visual puns, slapstick, and running gags (most of which aren't funny enough the first time they appear), Scary Movie 4 actually seems to have too much plot. It drags out almost like all David Zucker wanted to do was get through it. He throws in a couple of Airplane! and Naked Gun self-references, for anyone who might care that is, for himself.