- The episode "Johnny Test: Party Monster'', mostly the ending (although at least Dukey is spared).
- Dr. Wacko.
- The Deranged Animation in the later seasons; specifically the frequent screaming.
- Genderflipped Dukey from "Roller Johnny" falls straight into the Uncanny Valley.
- The episode "Johnnyitis" where Johnny drinks an unstable isotope and almost blows up.
- Johnny's bench after the F.O.T. (Freak Out Teacher) button is pushed.
- Johnny becoming a hulk-like beast after getting much testosterone in him in "Johnny Testosterone".Dukey: Okay, I'm officially scared.
- The episode "Johnny Double Coupons", just the idea that Johnny would risk his life or at least risk getting severely injured just for the attention of the neighborhood and the only people who got in his way were his sisters and Dukey. And then the sisters and Dukey let him try skateboarding down an incredibly large hill, that he has been repeatedly told will at the very least cause him severe injury. Plus ,His protective gear gets blown off leaving him rolling down an enormous hill practically defenseless. His sisters and Dukey do save him though.
- Also in "Johnny Double Coupons" most of the town are cheering for Johnny to ride down the hill. And even trying to make a profit off the event by selling stuff. But at least one of those people have to know that riding down that hill is dangerous.
- "Johnny's Royal Flush" has a disturbing scene where an alligator gets sucked into a sewer turbine and is promptly ripped to shreds, which is followed up by revealing that it got turned into alligator-skin bags.
- Poor Gil being very terrified when the now vampire Susan and Mary try to bite him and have him for the rest of eternity in "Fangs a Lot Johnny".
Nightmare Fuel / Johnny Test