Put Your Urine Where Your Mouth Is

On the internet, people use short little phrases like "brb" (be right back) or make little faces with different keys to show an emotion such as a smile :-) . There is even one for "put your money where your mouth is" that looks like this: :-$ . But here is my confusion, there is also a common "smiley" used that looks like this: :-P . Now, using what we have learned from our "put your $ where your mouth is" smiley face, I can only assume that the smiley, :-P , means "put your Pee where your mouth is." I don't know why people say this to me online. Not only is it rude, but it doesn't make that much sense.