Magic Detectors

Magic Detectors are devices used to detect the magic used by Fairies. These devices are usually deployed by Mr. Crocker in his never ending hunt to reveal the magical creatures to the world. Crocker's inventions are typically crude, unwieldy, and sometimes dangerous, though thankfully they are mostly only dangerous to Crocker's health.

TransParents
In his first appearance in the series, Crocker uses a "Fairy Finder" device to detect that the two beings posing as Timmy's parents are really Cosmo and Wanda. He attempts to employ a variety of traps to get them to reveal themselves, only to severely injure himself each time.

Dread N' Breakfast
When Crocker paid to spend a night at the Turner's bed and breakfast house, he wore a magic detecting device with many butterfly nets on it. Timmy wisely does not use any magic in his presence, keeping Cosmo and Wanda hidden until the very end when he was able to hide them amongst an army of reanimated sock puppets. Crocker's magic device was destroyed and he quickly fled the scene.