I meant "That's Okay" to Megan to ask questions later, not to the iguana as a service animal, lol.
I used to know somebody long ago who was "off" who took her iguana everywhere with her too. It could do no more for her than a stuffed animal iguana, so I would call it a comfort animal, not a service animal. She was definitely a lot calmer with it, in a literally off-her-antipsychotics kind of way, so we allowed it sometimes.
In past years the ADA did not have it specified what types of animals were service animals, so some people did have some odd ones, but merchants complained they could not be expected to reasonably accomodate every type of animal. It was financially an unreasonable burden, unhygenic, and sometimes bad for business. EMS workers complained of a variety of issues trying to help people with service animals (like getting bitten). So in March 2011 the ADA revised the Law so only dogs qualify as service animals, and miniature horses only where facilities already exist to accomodate them.