Cologne is Shampoo's ancient and powerful great-grandmother. Cologne and Shampoo run the Neko Hanten (Cat Cafe), her Chinese restaurant.
Cologne holds Ranma responsible for Shampoo's curse, and tries to make Ranma accept his "marriage" to Shampoo. In the process, she subtly grooms her son-in-law by training him in new martial arts techniques.
Even though she is a withered old crone, she is vain about her appearance, and is not amused by jokes about it. However, she does seem to tolerate Ranma calling her "old ghoul".
She knows all her clan's secret martial arts techniques and magics, and has many arcane items stored away.
Entrance: Nettohen episode 3. Volume 5 part 6. Distinctive features: Hops around on a gnarled wooden staff somewhat like a pogo stick. Weapons: Her staff. Name: Not revealed until Happosai recognizes her much later, in Nettohen episode 37 or volume 10 part 1. Throughout Nettohen, she is listed in the credits as `o-baba'. The name ("possible" + "rugged mountain place") is meaningless in Chinese.