How to change back from baby on neopets?

You can change it back to baby, but you have to buy the brush, which is currently going for 600,000 on the Trading Post. If I were you, I'd just keep it as a baby, because Faerie Paint Brushes are going for 1.1-3.5 million on the TP. If you really want to change it from baby, try using the secret laboratory map, than zapping your pet. Beware though, the map can do negative stuff too, like lowering stats or changing your pet from a beautiful royalgirl ixi to a mutant grall.