Bye Butt!
Bye Butt is what you say to your family when you leave the house. "Bye "refers to the fact that you are leaving, and "Butt" refers to your family members, who are all nicknamed butt.
Steven's Sister: "Where are you going?"
Steven: "The store. Bye Butt!"
Steven's sister: "..."
Steven: "The store. Bye Butt!"
Steven's sister: "..."