I’m online and I have multiple personalities. Not MPD, I’m just moody. Does that count?
Not multiple personalities per se, I was on a board years ago (long dead I should imagine), a guy on there took a fancy to me (he being about 5’2" to my 5’11-and-a-bit). It wasn’t a normal “phwoar I fancy her” type thing, but an ugly stalker fetish thing and he followed me around the internet for about 3 years, as I’d stupidly used the same name everywhere.
Once I copped on how he was following me, I started using different names for different sites, and had my name changed on old sites where possible.
In another situation I’d a friend who was a complete luddite who ran a boarding kennel. I suggested she get herself a website and email, she refused (convinced that the internet was all paedophiles and porn), so I set up a website and email address for her and would answer emails as her. She inadvertently ended up becoming a rehoming ‘shelter’ as well, so I impersonated her on some dog message boards for a while as well to find homes for the dogs
Years ago, there was a teenaged girl who participated in an AOL chat room. She was always involved in any drama was unfolding among the regulars, and started quite a lot of he drama herself. After a couple of years of this it turned out that Agnes was actually a man in his forties who managed a tire store in Florida.
I used to have a MySpace account for F. Scott Fitzgerald and would write back as if I were him when people contacted me. He had like 1000 friends or something. I think it’s still there.
I was 16 when I made it. I’m still a literary geek, but I wouldn’t go that far anymore.
Not pointed at anybody here, but I have suggested some people need to check Ebay and see if they can buy a life. It is their only chance.
Again, not in an attempt to fool anyone. I do have 2 LinkedIn accounts. One for voice work, one for my real work. Different industries, different links. I am, however, linked to myself.
Didn’t we have a thread a few years ago about some guy wanting assistance in creating his fake British persona for some message board he was on. It was a bit weird he was pretending to be some type of academic or maybe barrister I think.
Not exactly an alternate personality, but I do have slightly different typing styles on different message boards, in a probably vain attempt to keep people from linking me For example, I tend to rarely write one sentence replies here, but do it often elsewhere.
I also once took on a different personality when using one of those secret honesty boxes on Facebook to keep an old friend from figuring out who I was. (No, I wasn’t saying anything mean–quite the reverse.) She actually did figure it out, but I successfully got her to decide it couldn’t be me.
Yeah, when I was a teen in the 1980s on Prestel Daisy Chat, me, my brother and a friend created a mentally subnormal character called “Motorbik Mike”. He couldn’t spell and was obsessed with motorcycles, but actually only owned a beat-up BMX. He would make assinine comments and generally fuck with people.
Should we send more food aid to Ethiopia?
do yu want t talk wit me about motorbiks i like motorbiks they are grate
Yes.
No.
waht CC i lik 250 CC but 500 CC is beter also yu shud ware a helmet
Well played. 
I’m on a roleplaying board. Even when we’re not roleplaying, but talking about real life, we’ll often stay in character. I have 5 characters. 4 females, 1 male. I only really use one though, since it’s an admin account and I don’t want to re-login every time I need to do something administrative, but they are quite separate individual personalities. Some people know who is me, some don’t. The longer you’ve been on the board, the more likely you are to figure it out. Everyone else on the board is the same way. One thing I won’t do is have conversations with myself under the separate accounts.
Not online, and not quite a personality, but oftentimes at work I’ll get sucked into conference calls with people in other departments, some of which are daily or weekly and can go on for a few weeks or months. I’ll oftentimes adopt a unique “personality” or accent or whatever for the duration of those.
I’ve been Southern sniz, Mellow sniz, sniz who works from home and there’s always someone knocking on the door, sniz that speaks… very… carefully… , Corporate Buzzword sniz, faaaabulous sniz, among others.