Whoa, didn't see this one coming...according to TMZ, Jersey Shore's resident bad boy, Mike "The Situation" Sorrentino, has checked into rehab for substance abuse. 

Sources close to the reality star tell TMZ that, though Sitch had been showing signs of substance abuse in the past, "he was getting worse" as the most recent season of the series continued. Though Sitch's rep commented that he "has spent the past several weeks at an undisclosed location for much needed rest and recuperation after his extensive production and appearance schedule," other sources confirm that Mike is definitely in rehab, and he definitely has a problem.

His behavior on set, which is described as "erratic" and "paranoid," was apparently noticeable by crew and cast members, and even apparent in some recent episodes of the show. 

Jersey Shore, which just finished airing its fifth season on MTV, was recently renewed for a sixth season set to begin filming this summer.

[via TMZ]