When a man marries, he acquires in-laws.  The Boy had a brother-in-law with two children, who were foisted upon auntie and uncle to be cared for overnight.  "The two most harmless things in the world are a four-year-old boy and a keg of TNT."  Jackie could get into deviltry while you winked an eye and then, after he had nearly wrecked the house, he'd snuggle into your lap and say, "You love little Jackie, don't you?"  And you did: Teddy, though too young to walk, could make life merry.  He was hungry, so the Boy held a séance in the kitchen with a bottle, a nipple, and some milk, without successful results.

Finally, everyone was peacefully slumbering―except for the cat.  It created such a disturbance that the Boy thought it was the burglar who had been terrorizing the neighborhood.  He snuck downstairs where, between the Cat, a toy gas balloon with a grotesque face painted on it, and a statue, the Boy had more excitement than if there had really been a burglar in the house.  His fears were dispelled: the man they thought was the burglar proved to be the night watchman!

What was said about I Do:

Motion Picture News (August 6,1921 issue)
"Harold Lloyd is at it again―at it with a new line of comedy tricks which will make any animal or human laugh on the face of the earth."