There are two people on top of each other in bed

A five-year-old Mikey asks his Grandpa, “Grandpa, what do you call it when there are two people on top of each other in bed?”
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The Grandpa feels very uncomfortable but decides not to confuse the child and bravely says, “That’s intercourse, my boy.”
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“OK,” nods Mikey and off he goes.
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He comes back after five minutes and says, “Grandpa, that’s not right. I’ve just spoken to mom and she said that it’s not called intercourse but a bunk bed!”