How exactly do i do this? I remember one time i was playing a zombie match and i simply clicked where the words "Charlie Team" would be in a team match, and BAM. I was charlie. That doesn't work now, however.

/setteam3 player number

What hapened to you was probably a bug.
But in CTF you can already play as charlie, delta.

You have to loggin as admin and change your team, that is the only way.
This way works but you cannot score but you can pickup flags, even blue & red at once!

Cool, thanks!
Edit: You can also do this in infiltration!

Yeah its fun All the red and blue runnign around killing eachother and there all like to you HELP THIS TEAM PL0X!! and i just grab both of the flags and let them chase me,and then get kicked =.=

This brings up an interesting topic...do people mind when they're playing in a legitimate CTF match and Delta and Charlie are throwing a wrench into the works? Because I know I've enjoyed playing on Delta and Charlie before, but I kind of think the Alphas and Bravos resent it.

I'm pretty sure they dislike it, that's why i only use it for making CTF matches a little more... intresting. (with zombies on delta)

or on some silly servers just go !joinC !joinD
But normally its admin having a laugh.