Dale Tholen was one of the crop of specials builders that did Crosley proud back in the fifties and early sixties. His first build (currently owned by Bonneville racer Gerald Davenport, I think) was not only a terror on the tracks of 1955, it was one of the best looking homebuilts of all time- good enough to show up on the cover of Road & Track!
As great as the first car was, Tholen soon began thinking of improvements, and had another car built and on the track by the early sixties. That car was the ThunderMug, another good-looking hmod special, currently offered up for sale here. Once again Tholen created an elegant design, although the ThunderMug appears to be much more of a stripped racing thoroughbred than the comfortable boulevard racer the first car was. Tholen's 24 pound fiberglass body appears to owe a nod to contemporary Jabro designs, especially in the rear.
This time out Tholen foreswore the Crosley motor in favor of a handbuilt engine assembly largely based on parts from 3 Maico single cylinder motors. I'm assuming that engine was problematical since the car eventually received a Crosley powerplant, although the original engine is included in the sale.
If the custom powerplant perhaps underperformed on the track, it was responsible for the car's singular name- the engine's unique gurgling sound supposedly mimicked the sound of a flushing 'thundermug' (old-timey nickname for a toilet)!
Here's a link to a 1963 article from Today's Motor Sports.