In the pilot, first thing childhoodfriends, Adam and Derby do when they met eachother is hug eachother. Now Derby is not Adam's best student, but it shows they are good friends who have probably never seen eachother in years.
In Mr. Space, Adams friends tell him they do respect him as a teacher and he agrees to quit his job at the space program.
The final interaction between Adam and Cyber!Echo in Mr. Pixel.
Firdge Heartwarming. Since Derby designed the Cyberworld, he probably designed Cyber!Echo to have a crush on Adam.
In Mr. First Impression Echo kisses Adam. It turns out she has feeling for Adam and when she seemingly rejected his Declaration Of Love it was because she wasn't prepared.
It gets better in Mr. Kidd, they kiss again and it was enough for Echo to get her memories back that Mr. Kidd whiped away.
Though that's somewhat ruined by the fact that it works on everyone, no matter what their relationship with Adam is.
In the episode Mr. Memory, Ivy realizes Slab is the only boy in school who didn't ask her out and get rejected. So she tries to get him to ask her out, at the end of that subplot, Ivy asks Slab why; he admits he does like her but would never ask her out because he knows she would reject him. She says that she wouldn't and finally talks Slab into asking her out. She says yes, and the two kiss.
In Mr. Final
Echo saying the best thing to happen to her was hooking up with Adam.
Ivy calling Slab a good boyfriend.
Mrs. Byrne deciding to settle down with Master Ki.
The fight between Ki and Dang, where Ki chases Dang across the world, punching and kicking him all the way. Dang just stands there bored because he can't bring himself to hurt his Master.
Principle Tater's graduation speech.
At said graduation Slab thinking his was going to spend the rest of his life in High School is called up to recive his diploma, he is overjoyed.
Firdge Heartwarming In a previous episode, Slab befriended some college jocks and hoped to join them, and now he can.
After the graduation, Tater aproaches Adam with a list of his students next year, Adam says he wishes the next science teacher good luck, saying he only became a teacher so he can have the high school experiance he never had, and now aspires to be a college proffesor. Adam points out that Tater never wanted him as a teacher in the first place, Tater says yes and admits that Adam made the place fun for him.
At Adam's first day as professor, he see's his first class consists of his old class. He points out they passed science and don't need to take it,and realizes they are here because of him.