Each of the three dogs represent one of three dogs from Hanna-Barbera cartoons.
The one on the left appears to look similar to Big Dog from the cartoon 2 Stupid Dogs; however, this dog is wearing a suit.
The one in the middle is loosely based on Spike from Tom and Jerry, wearing a red sweater, a navy blue jacket and pants, and a flat turquoise cap.
The one on the right strongly resembles Astro from The Jetsons, but with a green sweater and khakis.
The canine Thugs were first seen after Scaramouche was telling everyone that he was on the phone and later insults the trio. The bulldog thug pulled Scaramouche's head out of the phone booth to tell him he would remove his head from his body if somebody did not already and tossed him in the ocean.
It is unknown how the past Aku's destruction affected their existence.
Bulldog: "YOU TALKING TO US?!"
Astro: "I think he's calling us dogs."
Bulldog: "Usually me and the boys would rip your head from your body! But it looks like somebody already did us the favor. So in lieu of that..."
- Ironically there was a "no dogs" sign for the ship and Scaramouche refers to them as dogs. However, they were only sapient beings and the restriction applied to real dogs only, in which they took that term offensively.