see a man about a wallaby 

go to the bathroom.

While it may be used in "Finding Nemo", Mr. Disney (who was deceased, by the way, when "Finding Nemo" was made) did not come up with it. It is an Austrailian saying which was popularized in the movie "Crocodile Dundee".

"Man, that was a great chili dog, but now I've gotta see a man about a wallaby."

see a man about a wallaby by ixolib December 10, 2008

see a man about a wallaby 

Take a crap, drop a bomb, drop some friends off at the pool, feed the porcalin, brown the water, kill a potatoe, make a deposit, feed the chickens, chop the firewood, weed the lawn, attack the castle, make an appeal, go windsurfing, see a movie, write an english paper, farfegnuegin, or make some chocolate. If you are confused, we're talking about pooping here.
The wallaby one is honestly from a Disney movie, "Finding Nemo". Man, Disney, good call!

Excuse me, I have to go see a man about a walaby. Keep rinsing, we'll start on the back molars in just a few.

see a man about a wallaby by stevie September 15, 2003

I'm gonna see a man about a wallabee 

an expression used by the residents of sydney, australia describing the euphoric sensation of wanting to pull your wang out and let it rip

(Eric) How was your flight?
(Ivan) It was long but i didnt really mind cause there was this fine ass bitch sitting next to me the whole time...now if you'll excuse me I'm gonna see a man about a wallabee

I'm gonna see a man about a wallabee by ivan dogg September 30, 2008