Cathy is chosen to show Sal Mineo around his old Brooklyn Heights High School, but Patty thinks the honor should go to her. Cathy relents and Patty gets a chance to act with Sal Mineo in a school play.
Patty falls head-over-heels for her new science teacher, Greg Noble (Robert Goulet) - and her studying genetics of 19th century scientist Gregor Mendel only serves to convince her that their genes are a perfect match, and being Mrs. Greg Noble is her destiny.
Ross' pet frog accidentally finds its way into Patty's bed. This triggers a series of practical jokes that eventually involves the entire family, whether they deserve the practical joke treatment or not.
Martin begins to feel he is losing touch with his daughter Patty and would like to spend more time with her. When Patty agrees Martin begins to realize that he may be getting more than he bargained for.
Cathy writes a letter critical of an editorial in her Uncle Martin's newspaper, not knowing that her uncle wrote the editorial. The resulting firestorm has Cathy worried about her future in the Lane household.
Patty, because of her lack of cooking skills, fears that she is losing Richard to a rival. So Patty enlists Cathy to cook for her in order to get Richard back. But the plan backfires when Cathy is called away before she can prepare the meal.
Patty's rival Monica throws a party but doesn't invite Cathy. Patty gets Cathy invited but at the expense of losing Richard on a date to Monica, so Patty decides to skip the party. That is until she learns that a musical group needs a lead singer and there is a possibility of a record deal at the party.
Richard's parents leave for a week so Patty invites him to stay at the Lane house while they are gone. Things seem to be going okay until some of Richard's actions begin to rub some of the family members the wrong way.
A friend suggests to Cathy that the Lanes wouldn't stop her from becoming an exchange student because she has worn out her welcome there. So Cathy decides to prove her friend wrong by signing up for the program.