In Funny Business, it is eventually revealed that Jeannette is actually self-loathing and has a massive Guilt Complex, and is only pretending to be a Cheerful Child so that her loved ones don't worry about her.
RWBY's Weiss is this. She prepares for a conversation with Schnee employees by practising a smile...which as soon as the talk is over, to be replaced by an unhappy expression.
Like the The Nostalgia Chick, The Nostalgia Critic also delves into this on occasion. Mostly when a movie does something good then completely fucks it up but also when he was talking about his parents.
*shows a picture of his kindergarten self being ripped apart by two monsters labeled "Mom" and "Dad"*
Quite a few of these have shown up in Survival of the Fittest, surprisingly. Most of these tend to be Type A, for obvious reasons. Some examples:
Former gamer Warren Pace gives himself a complete image makeover to fit in with the football team due to his perceived images of jocks.
Maria Graham has a bad habit of burying any pain and angst underneath an overly cheerful, energetic persona. It's already been shown before that when she finally crashes, she crashes HARD.
She ended up crashing pretty early once the game started, though she often tries to put it back up again. Eventually she succeeds when Duncan McMahon, her childhood friend and love interest dies right in front of her, causing her to finally lose her mind.
Hermione Miller also has been shown to have tendencies of this. She spends most of her run in serious denial, believing that she is at the campsite while acting eerily cheerful and rejecting all signs that she's stuck on a Deserted Island. Eventually she has a revelation about her situation and that no one will take her seriously due to her being The Ditz, and right after is Driven to Suicide. She also receives a fair amount of Lampshade Hanging comparing her to the Trope Namer.
In mini site Spin-OffThe Program, Brigadier General David Adams, the founder of the title game, is very much a (possible) Type C. He has been described as pretty casual looking for a military organization, and oftentimes slides into Cloudcuckoolander mode during announcements. However, he has shown to have a very chilling approach towards the idea of children killing each other, and seems to really be enthused by it. Needless to say, there's a lot of Dissonant Serenity in his announcements.
The Whites from Lucky Day Forever can be seen as Type B. They are always shown donning a smile on their faces, as if it's the only expression they wear on their faces. The only thing they managed to do is to trick the Proles into becoming their Human Resources.
Put the paper away, it's time to eat, Justin thought. Yes dear. Mmm. Smells delicious.
"Put the paper away, it's time to eat," Dorothy said. She was holding the coffee pot, stepped behind Geoff, putting a hand on his shoulder, and bent down to kiss him on the top of his head. Automatic, without affection.
"Yes, dear." Geoff said, smiling up at his wife. "Mmm. Smells delicious."
From Welcome to Night Vale: Literally all of the town Desert Bluffs, run by the evil corporation Strexcorp. In particular, the radio host Kevin, who on the whole is even cheerier than our usual Cecil, but reportedly doesn't smile right. Also, his studio is covered in blood and viscera.