THR reports that Will Sasso is a "likely frontrunner" (whatever the hell that means) for the role, and his name has been knocking around for contention for the past little while. Sasso is probably best known for his stint on "MADtv" and his current role in the series "$#*! My Dad Says." He's also been making strides into features, appearing in "Life As We Know It" last year and in the upcoming "Arthur" remake.
All this said, the Farrellys still have plenty of options. Hank Azaria was previously mentioned as a contender for Moe while Andy Samberg is apparently vying for Curly; Shane Jacobsen, Justin Timberlake, Woody Harrelson and Larry David are all said to have been approached as prospective Larrys.
These dudes need to make a decision soon if they're going to make their April start date for the ambitious project, which will drop the Stooges in the modern era, in a PG film that will be told in three interconnected, short films. The plan will also find the directors recreating classic gags, but re-interpreting them and re-contextualizing them a contemporary setting. No release date has been set yet for the film.