not a throwaway account but i actually just don't really use reddit that much
My friend had a Youtube channel. He would make his own videos and upload them all the time. I would help him out with them all the time. For about a year me and him and some other people would always be hanging out and working on his movie projects.
I made my own Youtube account and commented on his videos pretending to be his biggest fan. Then I started making "tribute videos" where I'd re-edit the videos that he uploaded. The tribute videos got progressively more and more creepy and threatening, and he started to get freaked out. Funniest part about it was that literally everyone but him knew it was me. Even his girlfriend eventually. He and I had a few really long conversations about who the sick fuck behind these videos might be and what his motive was for doing this.
At one point I thought he might've been catching on, so to throw him off my scent I got on Omegle and asked the first person I found to record a video of themselves reading a short script I'd written for them into their webcam so that I could upload it to the channel. When he saw the video, and didn't recognize the person in the video from school, he thought there was no way it could've been a prank.
To add to that I also tracked down his reddit account and posted screencaps of some stuff he said in some of his videos. And I filmed the outside of his house at nighttime and uploaded that too. He was pretty freaked out and stopped uploading videos to his channel, though I can't say for certain that this was a direct result of the hoax I was pulling.
Anyways, I sort of stopped uploading videos and it kind of fizzled out and like 6 months after the whole fiasco I told him it was me. He didn't even believe me at first until he saw that I was logged into the YouTube channel on my phone. He never really looked at me the same way since.