is it ever spelled "mega city 1" instead of "one"?

[mimikeke]

I'm painting up a poster and artistically it will look cooler to have a numerical one.  I don't feel like I've ever seen it written that way though, except when it's abbreviated as MC1.

Silly question I know

[Mabs]

I've seen it written both ways, my advice would be to go with the numerical one if that's what you'd prefer.