Unlocking All Players in Crash Team Racing?

I don't want to unlock them all by using cheats, but instead the hard way. For instance, I've beaten all of Dr. N Trophy's Time Trials but yet, I still don't have him. What must I do to unlock him and all of the rest of the secret characters? By the way, I am referring to Crash Team Racing for the PlayStation 1 console.

Suggestion:

A fellow CTR fan I beat the hell out of that game.
Pretty much you have to beat the game FULLY (adventure mode) every track, every gem, crystal etc, and as you do that, certain beaten tracks and obtained gems will unlock certain characters. As for you not unlocking N. Tropy, the only thing I can think of is that you might not have all the tracks. And in order to unlock him, you have to beat him in every track. If any doubt, try websites like the following: http://cheats.ign.com/ob2/068/011/011595.html

The only character I got through cheats was Penta Penguin