Fred and Mary got married, but can't afford a honeymoon, so they go back to Fred's parent's home for their first night together.
In the morning, Johnny, Fred's little brother, gets up and has his breakfast. As he is going out of the door to go to school, little Johnny asks his mum "Are Fred and Mary up yet?" She replies "No". Johnny says "I think I know why".
Knowing little Johnny's propensity for lude and crude remarks, his mum replies "I don't want to hear what you think! Just go to school".
Johnny comes home for lunch and asks his mum "Are Fred and Mary up yet?" She replies "No". Johnny says "I think I know why". His mum replies "Never mind what you think! Eat your lunch and go back to school".
After school, Johnny comes home and asks again "Are Fred and Mary up yet?" His mum says "No". He says "I think I know why". His mum replies "Okay, okay, do tell me what you think".
Little Johnny says: "Last night Fred came to my room for a tube of Vaseline and I think I gave him my airplane glue".