I was today years old when I found out you can potty-train an iguana. I'm in a Facebook group called "Derpetology" (it's hilarious, you should go join), and someone posted a video of their iguana using the toilet. In the video, it climbs up a homemade wood-and-chicken-wire device that serves as a combo ladder and toilet seat, and then does its business into the toilet. Wild! So I decided to do a little internet sleuthing and, bam!, "iguanas toilet training" is a whole thing! I just love stumbling upon new-to-me subcultures!
Here are some videos of folks training their iguanas to use particular spaces/areas like training pads, bowls, or other designated areas in their enclosures. And here's a video of an iguana learning to poop on a toilet. The video includes close-up shots of the poor boy doing his thang, and getting his "bottom" wiped. It also provides helpful hints to help you train your own iguana, including "Keep bottom centered," "Always be patient and gentle," "Be sure to wipe bottom," and "In the morning and after meals: Take iguana to the toilet." And finally, here's a how-to guide about potty training your toilet from the website Lizards101. My favorite piece of advice is:
Soak your iguana for as long as needed. If it's a normal poop time for your iguana, it will most probably poop straight away in the tub. But if not, try to soak your iguana in the water until it poops. If it takes too long and it doesn't poop, take your iguana out and try again later.