- The ending of "Lab Friends... Forever?", Billy, Zeke and Marsha having their own little slumber party (complete with pillow fights) after Marsha misses hers on earth. On top of that, Zeke and Marsha finally acknowledge Billy as a friend instead of just a lab partner.
- The plot of "The Date", Zeke and Billy trying to cheer up Marsha (who missed her chance to reunite with her summer crush) with a makeshift romantic dinner date is pretty sweet.
- In "Calzones", the ogre chef complimenting Zeke's cooking, saying that his calzones were the best he's ever tasted.
- Billy in general is just a big ball of heartwarming. The fact he would do anything to help and save his friends is quite Admirable.
- In "Sluggy", the montage of Billy and Sluggy bonding is surprisingly adorable to watch.
- While it's an off-hand comment, the story Marsha mentions in "Rat's Entertainment!" about when she was little (she was suffering from an "oozing rash", so her parents put on a musical to show how much she meant to them) is rather sweet. The people of Subterranea-Tania (even the villains) coming together to cheer up Anaximander, who repays them with a rockin' guitar solo.
- The ending for "The Battle For Subterranea-Tania" is really sweet. Especially when the citizens of Subterranea-Tania praise Billy and actually admit that he's a friend. (Or at the very least "Okay", for those those who don't really get along with him.)
Heartwarming / Billy Dilley's Super Duper Subterranean Summer