Ronald "The Lawn Boy" Miller (Patrick Dempsey) is the typical '80s movie high school nerd. He mows lawns all summer long in his Tucson neighborhood to save up the 1000 bucks to get a telescope, and while looking through it before buying it at the mall, he spies Cindy Mancini (Amanda Peterson), "the hottest girl in school" (of course!). Cindy is freaking out after spilling wine on her mom's best outfit and finding out it will cost $1000 to get it clean (again, of course!). The original title of the script was Boy Rents Girl, and that's basically what Ronald proposes: Cindy is to be his entry into the "cool crowd" by pretending to be his girlfriend for a month., in hopes that it will make him popular.
As the plot must move forward, Cindy reluctantly agrees (partly because she is in a long-distance relationship with Bobby, the star football player who's struggling at college), and after undergoing the requisite 1980's throw-your-credit-cards-down, clothes-and-haircut makeover, overseen by Cindy, Ronald slowly starts neglecting his loyal geek squad, and morphs into one of the shallow, self-absorbed popular students. Because they must be seen together, Ronald and Cindy start sharing the same space and actually start getting to know and appreciate each other for their respective traits. While Ronald is squarely focused on becoming popular, Cindy starts to develop feelings for him, but her hopes are dashed as the month ends and she and Ronald have a dramatic "break up" in front of the whole school. Cindy in genuinely hurt, and Ronald is genuinely an ass.
Ronald further alienates his real friends by hanging out with the jocks (who are always portrayed are jerks) and dating the hot chicks (who are always portrayed as sluts), and then, the ultimate insult: in one of the most emotionally overwrought scenes in the film, Ronald inadvertently goes in with the jocks, on the flaming dog crap prank on his best friend on Halloween. Later at a New Year's Eve party, Bobby pays his old high school buddies a surprise visit and discovers Cindy's "infidelity" with Ronald. Bobby's anger causes him to break up with Cindy, which in turn, hurts and angers Cindy enough for her to divulge the secret agreement she made with Ronald to all the party guests. As his classmates learn just how truly pathetic Ronald is, he is ostracized by not only the Cool Crowd, but the Nerd Herd as well.
Ronald's moment of redemption comes when he defends a nerd from a jock and shames the student body by pointing out they were once all friends, before the scourge of popularity splintered them into cliques. Upon seeing this heartfelt display, Cindy catches a glimmer of the Ronald that she was falling for, all those months ago and the end of the film finds she and Ronald literally riding into the sunset (on his lawn mower), as a certain Beatles' tune plays to fade out.
He will feed his flock like a shepherd. He will carry the lambs in his arms, holding them close to his heart. He will gently lead the mother sheep with their young. - Isaiah 40:11
