When you have sex with a girl while she is on her period. After you get your (Oscar Mayer) weiner covered in red (ketchup), you stick the meat between her buns.
So you have a weiner, ketchup, and a bun -- the nasty pornstar way.

the thing that you don’t have when you’re phones percentage is over 20

a combination of the words porn and horndog, therefore leading to someone who is obsessed with porn, and is also a horndog.

a porn dog is a man or woman that watches porn all of the time.

A horny person that uses porn rather than sex with others.