I met this guy on the weekend while checking out local garage sales. I was very intrigued by a bike he had clamped to his repair stand. It wasn't built up yet, but he's planning on setting it up with 26 x 4.0" tires . You should see what those tires look like next to a set of regular MTB tires.
It probably isn't bigger, but it's still pretty cool. The design is similar to the pugsley though, except the frame is symetrical (seatstays didn't need to be offset) since he's running a Rolhoff 14 internal speed rear hub. He had the rear dropouts and front fork spaced at 130mm so that he could put a fixed cog on the front wheel since it's threaded. That would be one mean looking fixie.