When they start bumping into each other like people at a comic con.
So what you are saying is make them completely devoid of girls? But full of nerds.
About tree fiddy
Depends on the scope of your game, if it's a tiny map then you'll only need a few and if its a giant game with 100's of maps then maybe thousands... You also gotta account for location, a city will have more NPCs than a small village. I'd say go with whatever feels natural in your game, and make sure they don't all start sounding/ looking the same!
It's a town map that's 55x36. With large buildings only 8 people. Not counting guards on the wall. And I just realized I can't show a pic here. I made sure to use a different sprite. Even made a list. Don't have any voice acting.
Please do not use Status Updates to ask Support questions, that is not their purpose. Especially as the answer is 'it all depends' which leads into a bigger conversation. There is a thread in General Discussion about making towns come alive, maybe that will help you.
When you think it's too many.
Separate names with a comma.