So I figured this out after watching Yoda in her cage for a good month. I noticed that before she goes to the bathroom, she/he sits on top of her/his ledge and stares at the water bucket below for a long time - it's like she/he has to think about it first. I'm not sure if it's because we keep telling her/him that she/he has to go poopy before we let her/him out. I dunno, I just wanted to share this with every one as a funny story. My other iguana Reiji, goes on her paper.
When I had a iggy she was same, I would tell her to poop in water before she could come out and she usually did. Iguana's are highly intelligent and can be taught several different commands. If mine was out and looked like she was going to poop on carpet. I would tell her NO and point to the paper I had put down, and she would do it on the paper.
That is very cool. I've been working on the "poop" command as well as "No" with both my iguanas. My other iguana, Reiji seems to respond well to my Nos, although sometimes i have to put my hand in front of her to stop her from going somewhere. What I thought was cool, was when I take Reiji out, I haven't needed a leash for a while now. She does get frigidity if i sit too long in one place, but for the most part she just roams around on me or sits on my shoulders/head. Both of them love car rides.