The special Fade Costume can be won from level 60 of Progress Goals. The retiredInvisible Costume is 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, Invisible pets clearly aren't... well, invisible. Fade pets start out with a dark color scheme and it becomes desaturated, fading in and out.