This achievement is story related, so you can't miss it.
*** Spoiler - click to reveal ***
After Laverne has her tentacle costume have her go outside. On the right of the former motel is a fence with a cat trying to crawl under it.
Flush the Booboo-B-Gone to Laverne and go to the cat. It will flee.
Use the Booboo-B-Gone on the fence and stand back. The cat will now crawl under the fence and paint itself a stripe on the back.