I saw that a couple of days ago. Dumb and Dumber are working off of an adaptation of a comic about Lovecraft that was published a few years back which takes a lot of liberties with Lovecraft's actual history (as is, makes him look more like Sam Neill's character from "In The Mouth of Madness," or Tim Robbin's character from "Jacob's Ladder" than being the weird introverted leech he actually was). It's an... okay comic.
So what I'm saying is don't expect Dumb and Dumber to be shitting all over Innsmouth and Dagon.