You could just use the crease tool. You'll get some artifacts, but they're minimal.
Either that, or just stick with 2 separate objects.
www.stevenegan-cgi.com
"Your weapons are no match for ours! People of Mars, surrender!"
"Um, this isn't Mars. This is Earth."
"Earth? Earth-with-nuclear-weapons Earth?"
"Yes."
[long pause] "Friend!!"