After Steve and Myra survive a near-death experience, he realizes how much he really cares for her and decides to give up chasing Laura (for now, anyway) and let himself love Myra. He then gives her his Science Club Pin, and they kiss.
And the reason why they're in Russia and he isn't? In a previous season they abandoned him for a research project. That episode ends with the Winslows agreeing to look after him while they're gone.
Eddie letting Waldo know, in no uncertain terms, that they'll always be best pals no matter where they go after high school.
Waldo discovering that he is an excellent chef, which gives him a chance to be more than just the neighborhood idiot when he goes off to culinary school.
Waldo's defeated, repeated, "Aw, gee," when Maxine mistakes Eddie's messing around to mean that Waldo is too, and you see how broken up he is when he thinks the girl he loves hates him.
Eddie accidentally throws one of Laura's cherished dolls away, so Steve spends all of Christmas Eve looking for it at the dump. He finds it with the help of a dog.
Carl shows up for Steve at school when his own dad wouldn't, and Steve, in surprise, responds with "BIG GUY!" and glomps him.
Steve starts a drive to save a classmate of his who has leukemia, despite the fact that the guy is always bullying Steve. At the end, the classmate thanks Steve and offers to buy him lunch.
In one episode, Steve plays poker with Carl and his police pals. He initially loses badly to Murtaugh and didn't know they were playing for keeps. Carl gives Steve his own money to make him happy, but the nerd decides to get back in the game and get back at Murtaugh. He wins, even taking Murtaugh's prized watch in the process, but he opts to give it back.
Steve: I play for fun. Murtaugh: You're all right, kid. (salutes him)
At the end of the episode, Carl and Steve opt to cut the cards for a little bet. Steve has to stay away for six months if Carl wins, but can come over whenever he wants if he wins. Steve draws a three. Carl then draws, and he (and the audience, but not Steve) see that he's gotten a face card, but he tells Steve it's a two.
In the Gun Safety episode Steve despite normally being a coward, has the guts to stay by Laura's side so she didn't have to go to school alone when a bully threatened her with a gun the day before.
Upset, 3J hides out in the Winslows' attic. When they find him, they announce that they want to be his foster parents, and will speak with his case manager. Before he goes to share Richie's room, he hugs Carl and Hariette.
In "Presumed Urkel", Steve faces expulsion when a science lab he was working in is blown up. Who defends him? Laura does, who has a lot of reason to dislike Steve. And Carl, who has dealt with Steve's mishaps more than anyone testifies in court, he tries to downplay the damage and also points out that while Steve has done damage, he's never lied, so if says he is innocent, he is innocent.
In the last season, the episode when Eddie decides to become a cop. Earlier in the episode, Carl was less than thrilled to hear this, and an argument ensued. The Heartwarming Moment comes when Carl takes Eddie to a bar, points out former cops who have been maimed in the line of duty, and asks Eddie whether he still wants to be a cop. When Eddie says yes, Carl tells him to stand up and introduces him as the newest member of the force, to the applause of everyone present. Doubles as a Moment Of Awesome.