Doing a Richbird
A form of sea-gulling involving your parents.  The person in question hides in their mum and dad's room, watches them having sex, and once his dad has finished, the subject runs out of the closet and ejaculates on his mum and dad.  He then runs around the room waiving his arms in a bird like fashion. 
Shit Rich! I can't believe you sea-gulled your mum and dad...
You sick Richbird.
Fancy doing a Richbird on ma and pa toinight?
I can't believe that little shit richbirded us!