Billy Phaidin

Billy is a book-only character whose "freaky flaw" is that he's invisible.

He was the second RAD to be sited in a 60-year span (the first one was a pack of werewolves back in the 1940's). In the book, he has a crush on Frankie Stein. He saves Frankie from the humans after by carrying her out of the school, so she looks like she's floating. He also gives her a rose to show he likes her. It is shown that Frankie does not like him back. He wears a name tag that says BILLY on it so people know he's there. In The Ghoul Next Door it is revealed his last name is Phaidin, as in "fade in". He also dresses up like Frankie to get everyone off her trail. However that had failed due to Brett's bad timing. In the 3rd book, Candace gave him the idea of making him "visible" by fake tanner, contact lenses, hair dye, etc. When he revealed himself to Frankie, she said he looked just like an "abercrombie model." Though they went on a date together, he realized she was still in love with Brett and gave up on her, only to be found flirting with Spectra Vondergeist at Clawdeen's party.

Billy is so far the only male character to have a chapter in the books centred around him.

A character named Invisi Billy made an aperance in a webisode of monster high volume 3, is asumed that is a version of Billy Phaidin.