A female small enough, that while having sex with her, you can hold her with one arm and walk to the fridge and grab a beer at the same time.
Brad was with John and saw a short good looking girl at the bar. Brad knowing he could walk to the fridge and grab a beer while having sex with her said: "oh man look at that hot fridge koala over there!"
A dildo that is highly popular in Australia, mainly amongst the aborigines. The whole dildo is carved out of eucalyptus wood, the tree that koalas get their food from. The shaft is similar to a didgeridoo and the head is shaped like a koala, hence the name, Wooden Koala.
Australian #1: G'day mate, how was your night?
Australian #2: It was great, I used a Wooden Koala on my bunghole. Now I can barely walk!