I havent actually thought and even writed about it but im having ideas, in this au AvA and AvM exist in one universe so Red has experience of being possesed three times
So in the au TDL somehow survived TSC in AvA5 and also somehow left bits of his own code in the colorgang when we deleted them slash eliminated them, bits of code that gave him access to the color gang files finding a way of entering Reds body in the process
So he started using Red as his avatar to interact with the color gang and others, but and Red? He was there, all the time, he felt like Yellow in the Lucky blocks episode, something like that, me thinks spectating what TDL was doing with his body
After a not long while TDL wanted to go back to his own body but... he didnt how to leave Red's first, and he started to freak out because he didnt want to be trapped in someone elses, so real
Then he told the color gang that he wasnt Red and that he was actually TDL that got trapped in Red's body and then they tied him to a chair because we know what happens when Red is not Red!! And they belived that TDL died but his soul got somehow in Red body because similar colors
Thats all sillies, I'll might write or draw about the Au more, cause I love this theory about TDL comeback by possesing Red (We know what you are Alan) /lhj