Posted this on Twitter, but kinda wanna post a longer more detailed version here. Might at some point write up other theories and readings for YBG on here too, but we will see~
Long ramble on a theory I have had for a while (2021-22ish)
Your girlfriend game (abbreviated to just YGG from this point on) is actually going to take place before YBG. Twist will be TK was the Y/N of that game. Perhaps canon ending being they got out by divesting themselves of you the player & running away to where they work now. (kinda hammers home that you the player are one of the antagonists of the story to have an ending where they do that too. Like YBG having the hints and YGG spelling it out for you in case you missed it).
TK says at one point they know first hand what it's like dealing with creeps & seem to have move to a dead end job/bad neighbourhood despite having a loving & supporting family. Were they running away from someone? (Sarah?) Plus they pick up on Peter real quick. Could that be from having a very similar experience?
Other possible twist. Peter has a cameo in YGG. Real brief though. We're talking shows up at Sarahs home uninvited to get something. Maybe they have an argument that you can vaguely overhear but at first you can't even see him. Then she brings him in to get the thing. He sees you, all out gawks for a bit saying very little and she kicks him out again.
Basically he see TK/Y/N aka YOU, so he actually has the first feeling of falling in love for the very first time ever. Something he previously didn't think he was ever going to experience. (but he doesn't recognise what that is as never had it). And him finding you miles away was him trying to track down TK/original Y/N sometime after the events of YGG once he realises what it was.
But by the time he caught up TK was already divested from YOU the player & was by rights their own person, so he ended up finding the new Y/N instead. (all planned by the creator of course since they like to see themselves as an evil mastermind) He never connects the dots neither does TK as they would both look very different by this point/first time they meet it was brief.
The majority of the game, perhaps even most endings you wouldn't know it's TK. Maybe the Peter cameo could even be in some routes but it would be a great way to tie the games if YGG ever gets made lol.
I just think it would be an explanation as to why TK seems a bit different than the other 3? + them dying the hair green as a way to customise themselves in a way is a cool thing. Like making themselves their own person. Since Y/N is like a blank template. TK also shares somethings in common with Y/N. Being none binary, having or had to deal with a creep.
Plus, by different than the other 3 I mean they are the only one that hasn't been written to do anything untoward towards Y/N (lol wording). If anything they can ONLY be helpful. Don't really need to say anything about Peter but the other 2 aren't exactly innocent. Spoilers and these are things that the creator could change or go back on but Don has apparently been taking photos of Y/N and being creepy with them. Plus Lucy's sex scene could be read as just non con or dubcon. When you are very vulnerable she gets you drunk/high and then the next minute is on you when you don't actually have the option to consent. TK doesn't get a single hint that their inclined to do anything creepy toward you. They instead go out of their way to assist, kinda like they've been through it before and want to lessen the burden for you.
I feel like it's important to note that all 4 of them know they are in a game. Below image for evidence and to be honest I feel like I could post a whole discussion about the below too. Worth noting that my read of it is the 4 know they are in a game but Peter is the only one that doesn't reset ever and is therefore basically tortured by the game and may have even changed the game in small ways.
I think the games evolved and changed overtime, which is natural for any game in development. And while I believe YBG was more fully imagined first, I can see as it was becoming a more solid concept that YGG would get built up too. Giving the other 3 sentience opens it up to the idea that they could get up to shit too. So, the idea that TK was a Y/N that kinda said fuck this and bounced and made a place for themselves in this weird fake world isn't all that crazy.
Also cool take on self aware AI being like no fuck this narrative but then getting condemned in a different way because these are horror games after all.
Example of TK as a Y/N that I drew in 2022 when I first put down my thoughts on this being a possibility to show the vision lol. They would work well colour scheme wise as they could very easily use the opposite colours while maintaining a bland enough base for you to project your character on to. Not that Y/N has a model in game, only ever art outside of the game, but you get what I mean lol.
I like them having their beanie instead of the cap! Plus them keeping it for a bunch of possible reasons. Remind them where they came from, or as a comfort thing. And the glasses work well in place of eyes and having th Y/N wording on them while still mixing up the design so that there is a definite divide between the two games and the Y/N despite being a vessel for the player still feels like their own character.
I also wonder if the candle tattoo is a hint to them having been a Y/N?
Side note lol: Worth noting TK didn't always have freckles & still doesn't in game but I like to think of them & the tattoo as ways in which they have made themselves their own person. Same with the piercings and green hair. I can't be sure but I think the candle came a fair bit after too, as the creator was ironing out their own stories.
Tattoos can have meanings and a quick google search of a candle tattoo (which another side note, since they have no other visible tattoos and a candle is so fucking specific I feel like it HAS to mean something to the creator to give them it in the first place)
Possible meanings found when googling:
More than the sum of it's parts. Candles are just wax and wick and yet they are capable of producing light etc. In my reading TK gave themselves this as a reminder that they are more than just a Y/N, more than an empty vessel for the player. They have made themselves a person with just a little light (power) from their own actions.
A light in the darkness. Something people might get that have dealt with bad times in their life, they have managed to get through and found the light for example. Links in with something bad happening to them before the game as discussed earlier. Something that keeps them going. It being on their back does also show that they are literally leaving it behind them.
Or admittedly, it could solely be to represent that they are the light for the player. Since they are always so helpful etc lol.
I just think if this was a thing it would be a neat twist that would better connect the games while also adding to the horror of it all.