On 30 October 2008, Rick Pirelli, Scott Beaumont, and Thad Steiner went to Tozier's Costume Emporium and bought costumes. Rick's got a werewolf costume, Scott got a Frankenstein's monster costume, and Thad's costume looked like "some sort of cross between a mummy and a ghoul.
On 31 October 2008, the Hervoken used their magic to possess Jim Tozier and make him wear a scary clown costume. The Tenth Doctor freed Tozier from their magic before he could scare anyone. Later that day, many children wearing costumes gathered at the Halloween Carnival. The Hervoken used their magic to transform the children into the vicious monsters they pretending to be so that they could murder their parents and themselves. The Tenth Doctor used his sonic screwdriver to destroy the Hervoken technology and turn the children back into children. (PROSE: Forever Autumn)
During the Halloween when the Cerebravores attacked New York City, Cindy Wu wore a skeleton costume. One man was affected by the Cerebravore emotion field and became terrified of some children in Halloween costumes.
On the afternoon of this Halloween, the Cerebravores possessed many inhabitants of New York and transformed them into their greatest fears. Because the possessed resembled people in Halloween costumes, AMNN reported that the incident was simply a "riot caused by Halloween revellers". (COMIC: Revolutions of Terror)
The inhabitants of Verticulus also wore Halloween costumes. When the Eleventh Doctor and Amy Pond celebrated Halloween on Verticulus, Amy dressed as a witch while the Doctor dressed as what he thought was the scariest thing in the universe: himself. They encountered two children dressed as a Dalek and a Cyberman. (COMIC: Wholloween)