A street gang causes trouble for the Winslows, and things become personal when they vandalize Rachel's Place and attack Eddie. Carl wants to take matters into his own hands, but Urkel decides to infiltrate the gang to trick them into confessing.
Mother Winslow regales Eddie's classmates with tales of her late fighter-pilot husband and of World War II's Tuskegee Airmen. Urkel's prison pen-pel shows up, not aware the picture he provided her is of Carl.
When squeaky-clean Laura enters the race for student-council president, snooty rival Cassie Lynn vows to gather dirt on her. Meanwhile, neighbors elect Harriette Neighborhood Watch leader, and Carl is down in the dumps about it.
Hoping to win Laura, Urkel strikes a deal with R&B singer Johnny Gill: his treasured baseball card in exchange for serenading her; Carl and Harriette discover that their honeymoon love nest is of the outdoor type.
Urkel's stay at the Winslows brings chaos when he swallows a fish that Carl was "fish-sitting", urges Richie to fight a preschool bully, and drives away Laura's study mate, Mark (if that's his real name).
It's hasta la vista to the criminal element and "hello, Urkelbot" after Urkel revives his robot for law-enforcement use in solving a rash of convenience store robberies on Carl's beat; meanwhile new shampoo changes the women.
Urkel plays bumbling, hard-boiled gumshoe Johnny Danger in a 1940s film noir spoof with Laura as a sultry client who needs protection for her aunt Rachel, a singer and supper-club owner marked for murder.