From Homestar Runner Wiki
Hollerin' Jimmy's is a brand of child's hobby kits sold at Bubs' Concession Stand. The basic hobby kit's total cost is "fifteen-tooty-two", which was paid by The Cheat in the form of pencil shavings. It is also a proud sponsor of "The Homestar Runner and Doreauxgard Show". The slogan is "We have no idea what's in this box!!", and, according to the side of the box, it is "not new!"
In Happy Hallow-day, when Halloween night goes missing, Bubs attempts to sell a Hollerin' Jimmy's Hovercraft Kit as a Halloween Night Hovercraft Kit. Its slogan is "There is no way this thing really works!!"