Ketchup and rubber buns

DAD: “Ok, so after every question i ask you you must say ketchup and rubber buns”.

KID: Gotcha.

DAD: what did you buy at the store?

KID: Ketchup and rubber buns.

DAD: What did you have for dinner?

KID: Ketchup and rubber buns.

DAD: What do you do when an old lady crosses the street?

KID: Ketchup and rub……. HEY!