Also, I know quite a few people who have special shadowramas made to fit the bottom of their TV screens (made from the stickers) simply to prop up when watching a Rifftrax. I think there's something people like about those familiar voices and the mental connection to those 3 specific characters that really draw people to the MKB riffs and shy them away from anything unfamiliar.
I actually think one of the things that keeps me into ICWxp is the fact that there's visuals to let me make a connection to a character or the person voicing the riffs. The same goes a lot of the time for even movie commentaries in general. There's a Hitchcock commentary I had a hard time sitting through until I watched a video with the guy who voiced it.... now that I know what he looks like and can mentally picture him, I don't have any problem with the commentary anymore.