Reviews provided by RottenTomatoes
New York Times:
Even by the proudly vulgar, dumbed-down standards of the Farrelly Brothers' novelty products, Say It Isn't So is an uninspired dud.
Boring, distasteful and predictable with brief flashes of wit that don't occur frequently enough to make the wait between chuckles worthwhile.
These aren't really jokes in the sense that something funny is happening. You're mostly expected to laugh at the idea that there are people who aren't laughing, which is just shallow and incredibly easy.
A horrifyingly moronic comedy that is boring rather than outrageous.
The movie keeps coming up with new ways to jolt, pelt, humiliate, and generally torture its characters, yet there's so little pace or invention to the way it's all staged that the synthetic mock cruelties barely register as jokes.
Say It Isn't So is the kind of movie that makes Dumb & Dumber and Kingpin, a couple of early Farrelly Brothers movies I was not fond of, seem like comedic triumphs.
The movie doesn't understand that embarrassment comes in a sudden painful flush of realization; drag it out, and it's not embarrassment anymore, but public humiliation, which is a different condition, and not funny.
Not even the beaver jokes are funny in this rangy, uneven Farrelly brothers rip-off.
San Francisco Chronicle:
Stroke jokes, prosthesis jokes, jokes about body hair and smells, and jokes involving the private parts of cows can't keep this one afloat.
Poor timing and muffed set pieces are compounded by implausibility and inconsequence.
The film elicits not the voluptuous discomfort stirred by the boys' best corporeal shenanigans but creeping embarrassment for everyone on screen.
The jokes about dead animals, gunk in the hair, incest and all other taboos are flatter than the road kill Gilly finds himself picking up for a living.