The Invisible Costume is a retired costume from the March 2017 Account Upgrades. Putting this costume on certain marapets will make them have a unique coloration behind some sort of fog. Unlike the name should suggest, the pets clearly aren't... well, invisible. There was already an Invisible avatar and that has been changed to 'Blank' with a new solution. If you already had this avatar before, it has changed to 'Blank'. There is an Invisible Paint Brush at Neopets, and if you back up a bit, they look very similar. The Invisible Account Upgrade package was going to retire April 30th, but it had been put back on sale for 3 days.