Sleepwalking Urkel takes out his hostility toward Carl in unusual ways. Carl becomes even more frustrated by his neighbor's constant visits at unusual hours, just to beat him on the head, snarl at him, etc.
Fed up, Carl complains, prompting Harriette to suggest hypnotizing Urkel to find out the root of the nerd's behavior.
After questioning by the doctor, it's revealed Urkel had destroyed Carl's prized model ship, which Carl had worked on for months. Seems Urkel, dressed in a suit of armor, had come over to show off his Halloween costume and knocked his lance into the ship (which Carl left prone on a table).
Carl yelled at Urkel for his clumsiness and kicked him out. But just after walking out the door, Urkel overheard Carl venting his frustrations to an agreeable Laura about the clumsy, nerdy, pesky neighbor.
Carl insists he didn't mean for Urkel to hear him say those things, but Harriette says the fact is, he did, and now he's hurt. Both she and Rachel give Carl the silent treatment until Carl apologizes.
That happens when Urkel returns the lie detector machine to the Winslows and hooks Carl to the machine so he can get the truth about their relationship out of him. Carl admits he isn't crazy about Urkel but he does say he cares for him. He then admits that he should not have said those mean things about Urkel and apologizes. Urkel accepts, just in time for Harriette to take over questioning her husband (and only leading to shocks).