After seeing Bonnie with her own car, Kim wanted to get her own as well. Since she could not afford one at a dealers, her father gave her his vintage Roth SL Coupe, which was a rusty old pile that seemed beyond repairing. Kim's younger brothers offered to fix and upgrade her car, but only if she agreed to give them rides whenever they wanted. Kim at first refused, but after many failed attempts to fix it up herself she reluctantly accepted their help.
When the Sloth was unable to keep up with a car that Motor Ed built from stolen Kepler prototype booster parts, the twins upgraded it yet again as a point of professional pride, calling it the "Roth SL Coupe 2.0". The newly improved Sloth was able to help Kim keep up with the Kelper and stop it, though it was virtually totaled by the combination of the Kepler's destructive shock wave, and wear and tear from the pursuit. This time however, Jim and Tim decided to fix and upgrade Kim's car free of charge.
- The Sloth bares a strong resemblance to the Lexus 2054 concept car, designed for the 2002 Steven Spielberg film Minority Report.