NPCs have come a long way since the original Half-Life. In that game, it wasn't unusual to have a Barney or scientist, who was following you around, get stuck on some easily avoided object or even just have trouble turning a corner. But the NPC's in HL2 are really impressive with their path-finding -- I only recall a couple instances my first time through the game where a squadmate got hung up on an object. Drop something in their path and they'll usually find their way around it.|
The friendly NPCs will also deliver lines of dialogue on occasion, or if you prompt them. Sure, they repeat after a while, but it can be fun to listen to them talk to each other. Prompt one to say something, and sometimes another in the vicinity will answer it.
For instance, someone might say one of these lines:
"I don't feel anything anymore."
And one of them might answer with:
"Could we talk about this later?"
Not every random line will match up perfectly with the random response, but for the most part, it works pretty well. Besides, sometimes when they don't match up, they're more enjoyable. Such as this line:
"Sometimes I dream... about cheese."
And this response:
"I wish I had a dime for every time someone said that."