The fake-i-fier was first used by Mark Chang to disguise himself on Earth, so he could remain hidden from his fiancee Princess Mandie, and to blend in with the denizens of Earth as well. The fake-i-fier frequently malfunctions when Mark Chang is threatened by affection or sweetness, turning him into various random objects or back into his alien form during inconvenient times.
The device looks like a symbol of six lines, each with a circle at their end, that meet at the center to form a snow flake-like shape. Sometimes when almost any kind of affectionate behavior comes into contact around or towards Mark, such as getting kissed, the device will malfunction and change Mark into a variety of objects.
In the episode, "New Squid In Town!", when Mark Chang arrived on Earth seeking refuge from his pre-arranged marriage to the violent and beautiful (ugly to him) Princess Mandie, he needed something to help keep him disguised amongst Earthlings. The fake-i-fier device did just that, turning Mark into a normal looking human boy. The device could also be used to change into a variety of costumes and monsters.
In "Wishology!", when Yugopotamia was invaded by the Eliminators, they stole the fake-i-fiers in order to disguise themselves as other people or objects, such as Timmy's friends. Later on, in the Abracatraz, when Poof smashes up a few guarding Eliminators, Jorgen and others steal the fake-i-fiers to pose as Eliminators and break out.
In Take and Fake, a similar device, deemed the iFake is seen resembling an iPod with the same symbol on it (hence the name), including with a shuffle function, and is used by Timmy Turner to attend Trixie Tang's costume party.