This meme first originated from facebook after a man (who was decisively drunk) decided to confront a woman he had asked out to tea 4 years prior and had been denied on the grounds that "she didn't like tea". He asked her if she liked tea, and when the answer was yes, he proceeded to yell "I FUCKING KNEW IT" she responded asking why he had ask and his reply was "I MOUNT MY PLATYPUS"
This meme is a sarcastic way to end your conversations as if you had more important things to do with your time, such as, well mount platy-pi.