The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
Carousel and A Little Heart To Heart would be Creepy Circus Music. As for why it's connected to tricksters, in addition to more direct circus-trickster connections like The Barnum and Repulsive Ringmaster, the stereotypical Snake Oil Salesman frequently associates with traveling carnivals or tries to invoke this atmosphere during their "medicine shows". Ergo circus music = someone has found their next mark.
Ominous Pizzicato Strings is a completely different thing from what you're linking; pizzicato is a weird "prickling" sort of sound made by plucking instruments that are normally made to be bowed. I remember seeing a thing from Mark Snow (the guy who did most of the background music/soundscapes for the X-Files) where he discribed it as "spider music". This is a good example of it (starts around 3:50 mark if it didn't do the timestamp thing right)
Edited by Scorpion451
So I remember that there's (or was) a draft in the TLP about a specific kind of music that tends to play whenever a villain, usually a Dastardly Whiplash or something, appears on screen. But I can't find it anywhere, nor I can't remember the exact examples included in the draft. Google's "hum to search" function wasn't much help, either. The closest I could find to an example that demonstrates this musical trope is "Carousel" from American Horror Story, or "A Little Heart to Heart" from Team Fortress 2. (Because trying to properly describe this in musical terms is practically arcane knowledge).
EDIT: Apparently, the draft I'm thinking of is Ominous Pizzicato Strings. Correct me if I'm wrong, though.
Edited by Unnerving_Posterior