Okay, so this has been going around, and I have a done a fair share of sharing it myself. But after the fourth or fifth somewhat luke warm response (wherein the comments were more along the lines of how funny Jack and Jill looked, rather than how hilarious the mash up was!), I realized, this is only really, truly sidesplitting to cinephiles of a certain ilk.
Why? For one thing, one needs to know, love, or at least sort of admire Hardcore, the George C. Scott contribution to the mash up. It is a grave-serious meditation on parental responsibility, guilt, the nature of evil, you know, the usual from fun-loving reformed Calvinist auteur Paul Schrader.
The juxtaposition of the most intense scene (Scott's father character watches a porno film starring his missing daughter) from that most intense of films with the willfully ridiculous new Sandler high concept mall-rat bait is, well, sidesplitting. And the fact Al Pacino, who probably redefines the word slumming with his appearance in J & J, regarded Scott as the greatest actor of of the generation before him, gives this an additional weird and wonderful meta-cinematic kick.