I was friends with all the people in How I Met Your Mother. They weren't real, they were still characters, and I wasn't an actor on the show, yet I was still there.
The premise of the show involved some forgotten events, and clues that reminded them of what actually happened. For instance, the fact that Ted found 3 plates of birthday cake reminded him that he had Barney were having cake in the hallway, when Robin came out with her own piece of cake. In my version of the show, everyone seemed to live in the same apartment building, so it was kind of like a dorm where people hung out in the hallways. Ted also had a set of another guy's clothes, and then he remembered meeting a cute curly-haired girl who had given him the clothes.
At one point, I was sitting on a couch with Robin, and another girl was sitting on a couch that was facing ours. I couldn't remember her name (still can't), but Robin remembered it, and said that was because they were both Canadian.
Then there was a dad with 2 little girls riding their bikes in the hallways. The girls also had masks -- not like Halloween masks, but weird Lady Gaga-type masks. We watched as the little girls rode their bikes into a liquor store (one of those liquor stores in bad neighborhoods where all the merchandise is behind bullet proof glass), and the owner, scared that he was being robbed by some freaky Warriors-style gang, shot the little girls.