The JOHNNY QUEST episode THE INVISIBLE MONSTER where the people would disolve that creature would CONSUME THEM, THE SEA HUANT with the creature stalaking through that cargo ship could you sleep on a ship with a monster in it?
Old thread I know but since Jonny Quest mentioned, I wanted to first second
The Invisible Monster (although the title critter looked like a Pac Man ghost when rendered visible) and
The Sea Haunt and say the following episodes of the various shows spooked me:
Creeping Unknown - An episode from the 1980's series. The Quests investigate disappearances in the Louisiana bayou caused by a kudzu monster. It sounds silly, but the actual creature is pretty freaking creepy, emits a very unnerving "oozing" sound, and engulfs victims whole like the blob. Later we find out that they are unharmed by this, which doesn't make it any better as they're put in big tubes and mutated into more plant monsters! And the part where the plant monster's human ally removes his gloves and he has green leafy branches instead of hands was just disturbing to me as a kid.
The Mummies of Malenque - Venturing into the Real Adventures here. In South America the Quests are looking for the Malenque, a tribe of Aztec-like Native Americans who died out mysteriously. It turns out a plague killed them and some loony scientist guy is harvesting the bacteria from their mummified remains to create a biological weapon. I was too old for this to scare me, but back when I was a kid, it would've, especially when the scientist tests the disease by spraying it into the face of one of his henchmen, and the guy turns into a living mummy and shrivels up. (A similar thing happened to victims of a succubus in another episode whose title escapes me.)
Undersea Urgency - Another Real Adventures episode. While Dr. Quest is investigating the progress of an underwater research center being built an earthquake unleashes a bunch of flesh-eating, coelacanth-like sea monsters. Nothing terribly disturbing in this like plant hands or people turning into shriveled mummies, but the wanton killing of unnamed extras - and some named ones, including the guy assigned to take the kids on a tour - is pretty unnerving. The monsters themselves are also walking, breathing nightmare fuel.
More Than Zero - Leave it to Jonny Quest to take the basic concept of a haunted house and take it to the next level, and the Real Adventures did love itself some nightmare fuel. The Quests become trapped in a famous haunted mansion in Italy after some other scientists' ghost-detecting whatever technology allows an evil spirit passage into the mortal realm. The most disturbing scene is the one where the guys who invented the whatever-machine are crushed inside a room with a lowering ceiling. It happens offscreen but just the claustrophobic horror of the idea is pretty frightening. Also the physical manifestation of the ghost at the end is all sorts of icky.
Also the ultimate fate of the bad guy in
Nuclear Netherworld....