To get the reflections to appear on one object and not the other, simply select the object that you don't want to receive reflections, and in the attribute editor (ctrl a) under the mentalRay tab. Un-check 'Trace Reflections'.
Heres an example:
"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?"
[long pause] "Friend!!"