Do you mean that some ppl have a witty comment in their whois, so you may see something like Dudly is dudly @ something.net Beware Masked Critters bearing gifts. In mIRC's options (options/connect) they put that witty comment on the "full name" line.
Or perhaps dudly @ this.is.my.superspecial.elite.arent.i.cute.com Give all cookies to bratty or else
In that case they are using something called a bnc. They can be named darned near anything. Basically they run on a shell, you connect from your ip to the bnc, then from the bnc to the network.
hrm. or do you mean is there a way to use more characters on the full name line in options?