Taken from a non-existent joke book for kids

Little Joey and his Uncle Bob sat in uncomfortable silence in the living room.

"Hey Joey, do you like jokes?" said Uncle Bob.

"Sure," said Joey, unenthusiastically.

Now Uncle Bob realized he'd put his foot in his mouth. All the jokes he knew were too dirty for an 8-year-old. He had to think on his feet.

"Ok, here's a good one. Two dictionaries escape from the library. While hiding, one says to the other," Uncle Bob could barely contain his smile during the dramatic pause, "one says to the other, 'what if thesaurus?' Ha!"

Little Joey winced and prayed his parents would be home soon.