What is the white stuff that comes out of crested geckos?

Answer 1

It's hard to say without seeing it and knowing which animal it's from, but if it's hard, then it's probably bone. Snakes swallow their prey whole. They do have quite powerful digestive enzymes but there are still parts of their food that they can't digest, so these pass through undigested. If the white stuff is fuzzy, it could be fungus (mold). If the white stuff looks squashy then it is urine or pee (this usually happens to lizards for Example Bearded Dragons, Geckos, Etc.)

Answer 2

Male Crested geckos will start to show signs of maturity around 8-12 months of age. These are signs that the male is now ready to breed as his sexual organs have fully developed. This white mess is a mixture of sperm, urine and is the males way of marking territory. They will usually remove the liquid, although anything left behind, will rub along branches and leaves, leaving his scent behind.