I'm a dude, but my roommate definitely had one of these, where he missed their AND MY hints that he could have a great threesome.

The roommate brought basically half the club back with him to the apartment, and we were all hanging out in the living room. He was missing obvious clues between both of the female friends he brought home were dropping (can we see your bedroom? can I get that out of your hair? what do you think of my shirt, can you tell I'm braless), and just as importantly he was missing the looks they were giving each other. They weren't just putting themselves out there, they were touching each other repeatedly, playing with each other's hair, and staring into each other's eyes.

So I sat directly beside one of the girls, and said "You and [she] should drag [roommate] into his bedroom, and both bang him into the sheets". She looked at me smiling, and whispered "Oh my god, should we? Do you think he's interested?"

As she whispered into her friend's ear, I walked past my roommate smiling, giving him the thumbs up. He was staring daggers at me.

The next day, two things happened. First, I bumped into the girl, and she flatly told me she really appreciated my nudge, but that she was glad that they didn't end up experimenting - they wanted to be business partners, and it was better not to have things complicated. Two, my roommate sat down with me, apologized, and asked me what my motives were.

I flat told him that I tried to set him up with a threesome, that the girls were interested (enough that they had 'the talk'), and that I was working to have his back the entire while.

He was pretty quiet for the rest of the night.