The Lost Room - question about Occupant

On the IMDb, there are two different characters/actors referring to
the Occupant:

Nathan Fillion - The Living Object/Prime Object
Tim Guinee - The Occupant - McCleister

There was more than one human object? Or was the Occupant someone
different from the Living Object?

I remember when Miller went to the institution where John Doe (the Object
formerly known as McCleister) was staying, I thought he looked very
different from the man whose face was shown in the polaroid that gave
a 360-degree view of Room 10. The latter had a more pointy face, the
former was more "pretty".

Why were there two different actors for this part?

Dano...

I doubt it. It's funny though, when I first saw that actor, I thought it
was Fillion too. The other actor, Tim Guinee does resemble him. I'm 99%
sure Guinee was the Occupant. I remember his appearance on SG 1.

IMDb is notorious for mistakes like this. I love the site, but you
sometimes have to take it with a grain of salt and an understanding that
fans contribute a lot of it's content.

Stan Brown...

I believe NF was originally scheduled to play the Occupant but had to
bow out.