Why is it sometimes when you pee in the toilet it foams up?

Question

Why is it sometimes when you pee in the toilet it foams up?

Answer 1

I think that only happens to boys when they pee standing up, the stream dropping from a height above the seat makes an aeration effect happen, force of the urine hitting the water makes the bowl water displace  and makes bubbles.

Answer 2

Likely, somebody cleaned the toilet recently and there was some detergent left in the water.

Answer 3

when u eat high protein food like chicken, fish etc and u dont digest it properly some proteins called mucoproteins that have not been digested leave your system by urinating. However, proteins do not mix with air or water so by passing through air and then directly into the water it creates this foam (concentrated bubbles)