I had heard of Tulpae/Tulpas/Tulpi/InsertPluralHere before, but I never really knew exactly what they were. So I read through the information linked in the OP and I got intrigued. I won't have to go through this Tulpaforcing or anything like that, because I've had something similar with me since god knows how long. He's been with me for as long as I can remember.
I used to think that he was just an imaginary friend. You know, someone an only child like me would make so that he didn't get completely bored out of his mind sitting at home with no one to do anything with. I noticed it was more than just an imaginary friend when I made friends of my own in school finally and he never really went away. He quieted down a bit, sure, but he never really left. He was always there when I needed him. Ever since my, I wanna say sophomore year in high school? (about 7-8 years ago) He stopped being quiet. He started being with me almost 24/7 and was always someone to talk to. I used to actually use him as a vessel type thing for RPing back in the day, back when that was all I did. Through said RPing, I had realized what his personallity was like, and his flaws and everything about him. Hell, I'd say that I know him as well as I know myself.
I've gone through the not-yet-mature stage of the Tulpa, because he kinda grew with me, so I wasn't even close to mature when he was getting there. Even nowadays, he's there for me giving me a conversation partner and such. I've gotten so used to him being around, I wouldn't feel right if I didn't have at least a small conversation with him once a day <.<
So yeah. I have a Tulpa and didn't know I did until now xD