Is there some kind of trick to this? I have tried extending conversations with various NPCs with the adlib button yet nothing happens. I know this doesn't work on every character but I can't get it to work at all. I thought in Desperate Times Kevin could at least ad-lib with Marvin or Rita, yet I get nothing when the official guidebook states otherwise.

Not sure whats wrong with yours... works fine with me...

You have to prompt a normal conversation by pressing x first. Once they say everything they need to they'll ad lib with you.

Tried that. I still get nothing. Very strange.

... then your game is bugged

I know that it does not work when you are using NPCs to interact with these characters. Only the original eight can get them to talk back.

Using Kevin... I'd say something is up with your disc. Notice anything else wrong with the game?

No, everything else works fine. The ad-lib commands work when I read a file or use the map, just when talking to NPCs I get nothing at all. Aside from this the game works perfectly.

By anychance are u using costumes or npc skins... costumes and skins wont let you adlib...

No, just standard characters, standard scenarios. Normal gameplay.

Gives me an idea for a video, although I had a similar one planned.

You have the PAL version of the game? Does both the ad-lib and audio work for that version? I can't remember, but I do believe there was some difference there from the American version since it has no audio for the ad-lib in F2.