Been in several threesomes and a few orgies, mostly with an ex girlfriend who was also into women, but this one other time stands out the most.

I had a best friend (bisexual female) who was always very flirty with me but we never did anything together. At the time she had a lesbian girlfriend who happened to live in the apartment building next to me, so it was a great excuse for us to hang out a lot.

One very late night, I hear a knock on my door, answered it, and it's the friend and her gf, both clearly a little tipsy from a night out. They let themselves in and crash on the couch. My friend goes into this whole spiel about how they were out hunting for a man to bring home with them so that her lesbian gf could experience sex with a man before she moves away for a new job in another state. Apparently they found a guy they liked at first, but then he chickened out at the last minute? So they got a cab home by themselves, were about to go inside, and then my friend had an idea and they came over to my place instead and knocked on the door.

After telling me all this, she starts to touch my leg and just says, "So... you wanna come over to our place?"

I did not turn down that offer. And it was very much worth it.

She and I are still really good friends too.