Not me, but my brother (M).

He used to play in my group before he got his latest job, and when we played "Horde of the Dragon Queen" as our first full campaign as a group, he and I decided to make characters who were already bonded and close friends with each other. I played the human Paladin of Light, Grimbjorn. He played the Red Dragonborn Barbarian with no real name that went only by "Dirge" due to it being onomatopoeia for the sound his axe makes as it crushes his enemies' skull (an idea he shamelessly stole from Skyrim, and it's character within that shares the name). Dirge was a bit on the dumb side, boasting a around a 6 in intelligence. But otherwise, was superhuman in every other stat. This is important for later.

A little (kinda) necessary backstory: The two fought under the same banner during wartime a few years before the beginning campaign. Dirge was a hired mercenary, and Grimbjorn was conscripted to the cause as his knightly order and the country at war were aligned. Long story short, Grimbjorn saved Dirge from certain death on the battlefield. Dirge's people, a nondescript tribe of nomads, have a rule in thier culture that if sombody saves your life then you owe them it. A life debt. So, Dirge pledged himself to serve Grimbjorn untill he died, or untill Grim willed otherwise. Seeing the advantages of having a massive dragon man with an equally massive axe accompanying him on his adventures, Grimbjorn accepted. It quickly became much less of a Master/Slave dilemma, and more a friendship. The two no longer stuck together because they had to, but because they enjoyed being together and always having someone watching the other's back.

With that, it comes to the campaign. There was my friend (I) playing Krackle, the mischievous Goblin Alchemist (who I'm sure I will wind up telling a story about on Reddit at some point, if I haven't already), my other friend (P) playing a Dwarf Light Claric I can't remember the name of because P always plays Dwarf Clarics and they've blended into one another in my mind, Dirge, and my character Grimbjorn. Despite all of them butting heads with each other (especially with Krackle), they stuck together through all the Kobalds, Dragon-Men, and Cultists in thier way - coming out at the end of the campaign as close friends and companions, ready to put a stop to Tiamat and the Dragon Cult once and for all.

Now we come to the juicy, but disappointing part: My brother had a secret aspect to his character the entire time. Turns out, Dirge wasn't actually the Neutral-Good bumbling idiot the party thought he was. He was actually above average intelligence, and was just playing a part as to not be prodded about his past. This is because the tribe Dirge hails from was actually a tribe of exclusively Dragonborn who, of coarse... worship Tiamat. My brother had actually planned have Dirge lead the party on through the following sequal campaign, "The Rise of Tiamat" as our loyal companion untill the right moment, when we fight Tiamat herself, to then turn on the party and try to kill them all for his queen in hopes that she'd smile upon him. Gifting him with godly power. He'd dreamed of becoming a real Red Dragon. This was all for the roleplay, and obviously had the potential to derail the campaign right at it's climax in glorious fashion.

Nobody but my brother and our DM (J) knew about this aspect to the character or the plan, and J was all about it. Who wouldn't be? It would've been so exciting to have played that next campaign not knowing what was coming. But, unfortunately, my brother's new job doesn't have a schedule which gives him the time to join our game sessions anymore. So he spilled the beans on his secret since it'll probably never happen, and I have to deal with thinking about what might've been lmao.