E-Cuck
A Cuck-E-Cheese is when three people go to a Chuck-E-Cheese for a quickie in the bathroom, while the third person stands on a toilet and laughs at them like it's the best thing ever.
They used the bathroom stall for a quickie while the third person watched from the next stall.
They had a full-blown sex session in the middle of the Chuck-E-Cheese while the third person took selfies.
They had a quickie in the bathroom, and the third person was on the toilet eating a pizza while watching them.