Shampoo has a bicycle that she uses to run deliveries for the Cat Café, a task that Mousse is not entrusted with due to his terrible eyesight and propensity to make mistakes as a result. Due to her recklessness, Shampoo frequently runs over others during her deliveries, most often Ranma Saotome. Although appearing in both the anime and manga, this gag is much more common in the manga continuity - in fact, it only appears once or twice in the entirety of the anime canon, including OAVs and movies!
Almost nothing is known about the bike itself save that it appears to be a pink single-speed bicycle with a basket in front. However it can be assumed that Shampoo bought it after she relocated to Furinkan and started the Cat Café with Cologne and her father in order to do the deliveries. She has demonstrated the ability to to literally bounce across the city with the bike, but does not otherwise use it for non-delivery related matters.
Mousse is also known to use a bike on a few occasions in the anime and manga, like Shampoo, he tends to crash into other people.