From Homestar Runner Wiki
Wormdingler is the name of Coach Z's dragon. First drawn in the Strong Bad Email dragon, Strong Bad criticized its lack of consummate V's. The dragon made its second appearance in Trogday 08, where Coach Z was celebrating its "birthday" and declaring it his bride, telling it that it does not need consummate V's. This was also the first time that Wormdingler's name was mentioned. A creature similar to Wormdingler is seen on Lil' Strong Bad's shirt in imaginary. Wormdingler appears on a Trogdor sketch sheet, as seen in a Tweet sent by @StrongBadActual on January 13, 2016.
Domicile: Coach Z's Locker Room (presumed)
As Coach Z refers to Wormdingler as his bride, he apparently believes it to be female. It has two eyes on its right side (or left side; it is mirrored in its original appearance) and an easily distinguished belly. It possesses a large head which tapers to a much thinner torso. It has jagged teeth, a forked tongue, and a worm or eel-like limbless body. It also has a slight underbite. According to Strong Bad, Wormdingler is not majestic.