- The entire premise of the show involves three kids around the ages of 12-16, trapped in a underground land filled with volcanoes, dangerous monsters, and a grumpy tyrant who wants to destroy the surface world with sludge. One might think about how worried sick the parents of those three kids are. (We know at least that Marsha's parents love her a lot, judging by the story she tells about them in "Rat's Entertainment".) Doubles as Nightmare Fuel. The episode "Surviving Billy" really shows it!
- The ending of "The Battle for Subterranea-Tania" makes this a million times worse when Anaixmander steals the Cheeserator and makes his way back up the surface world, leaving Billy, Zeke and Marsha underground far longer than the summer with probably no way out. And with no word on a second season yet, all we know, Disney may or may not have cancelled the show, and if they did, it would serve as a possible Downer Ending to the show.
- "Lab Friends... Forever?" has Marsha, being stuck underground, realizing that she can't go the slumber party that she was offered to go to. After being reminded about being unable to go to the party, Marsha runs off-screen sobbing. She does get better later.
- "The Tell-Tale Wart", Billy thinking that his Troggie friend Yucky has perished in a volcano whilst looking for his lost wart (which was actually taken by Billy). Although the scene may be narm to several due to Billy's long and obnoxious sobbing, it must've felt pretty bad for Billy to believe that his friend might've died at this moment. (Thankfully, He's still alive and well.)
- In "The Battle for Subterranea-Tania", after ruining the "Goodbye Party" and unintentionally causing a army of alien-robots to take over Subterranea-Tania, the townsfolk all turn against Billy, giving him a "The Reason You Suck" Speech, bullying him for his afro, and going as far to scream in unison WE ARE NOT YOUR FRIENDS!!! Billy may have messed up, but you can't help but feel sorry for him.
- Count Wretcher: Friends!? Because of you, not only we've been imprisoned and hit with electric whips, but you also said some really mean things.Gorkager: Yeah, when are you gonna get it through your thick-Hag Witch: Curly!Zartran: Red!Judy: Flakey!Thurston: Musty!Yucky: Yucky!Tony: Pleasantly shiny...?Gumbrump: Greasy!Count Wretcher: Wretched mop of yours!?
- Normally you'd expect a power-hungry tyrant like Count Wretcher to say something like that, but when it's someone like Judy, it's really heartbreaking.
- Billy's shocked reaction and the citizens growling furiously in response arguably makes this even worse.
Tearjerker / Billy Dilley's Super Duper Subterranean Summer