it was lil cartoon ppl that walked around n everything and we could have fights with eachother and there were all these different rooms....do you remember it...n if you do...do you know the name

Well, it definitely wasn't on mIRC.

What you are referring to sounds like a GMUD (Graphical MUD (Multi-User Dungeon)) (and not to be confused with the MUD client "GMUD" which is text-only). There are many of these, and none of them run on any sort of standard. They come in all forms, from 3DVR (virtual reality/vector rendering) to 2D sprite movement. These generally require specialized clients to access the proprietary server, as again, no standards have been formed.

There are many Graphical MUDs out there, so give Go[/co...d]e a try. The most popular appears to be Furcadia, but that's a different story for a different day.

- Raccoon

could it be Microsoft Chat Client?

There's something I know of similar but not exactly like what you've described. Try Habbo Hotel.

You create your character, and you can travel into different rooms in the hotel talking with people. You can earn credits and do different things.

Microsoft Comic Chat

The last name Microsoft used for that client was "Microsoft Chat" (version 2.5).

In any case, the comic characters could not walk around, so I don't think he's referring to that client.

You could make your particular character perform actions like being mad or happy or slapping somone around abit with a large trout.