You can sign up using any acceptable name you want. We have a @jessica, but if you want to be jessica-2 and use the same character image as your avatar, go for it.
However, as new episodes air and new characters are introduced (or old unnamed ones named), there may be users signing up with character names before they can be added to the site. If this is the case, sorry, but I’m removing your account. Save yourself the trouble and choose something else. This is a Ricktatorship.