heys! how long has your little ig not been eating for? Has he been to the vet at all? If not, you should take him so they can check for parasites. Even if he doesn't have them, a good reptile vet will be able to tell you if they're is a medical reason for why he's not eating. Other then getting a new reptile, is there anything that may have stressed him at all? A change in his routine or anything like that? Seeing the frilled dragon could have done it tho, maybe he's jealous
. Stress will make iguanas stop eating. Force feeding, in my opinion, should only be used as a last resort, and could stress out yer ig even more. If it hasn't been to long since the last time he's eaten you could try feeding him some vegi baby foods, or greens that are cut up really small. You could try adding beet juice to his food because some igs are attracted to the color. Try giving him foods that you would normally only feed as a treat, and see if he eats that. Keep drinking water in the cage all the time, and try giving him warm water soaks if he'll let you. If worse comes to worse, and he won't eat, you could try hand feeding him as long as that won't just stress him more. Wait for him to get calm, then offer him some food. If he won't eat it on his own, then when he opens his mouth put a little part of the food in there. I had to do this with my iguana before. Once a piece of the food is in their mouth, they will most likely eat it rather then spitting it out. Feed him a little bit like this if you can, but also continue to feed him in his cage so he can eat himself if he wants too. Watch for weight loss, dry, shriveley looking skin, and behavior changes. Iguanas can get dehydrated very easily when they stop eating. Good luck! i hope your iggey starts eating soon! Tiamat sends lots of feel hungry soon headbobs to yer ig! 
~Chelle