Hell's teeth! Check out Katy Perry's single cover

Katy Perry ditches her usual sexy look for braces, glasses and a pair of fluffy slippers.

The 'Fireworks' singer completed the geeky look with a plaster on her knee, a roll-neck top and a denim waistcoat.

She's also had old-fashioned metal braces fitted and wears her hair in a schoolgirl plait for the cover of forthcoming single 'Last Friday Night (t.g.i.f)'.

The singer is likely referencing her teenage years, during which she was teased for her looks.

She recently tweeted: "In middle School they called me "over the shoulder boulder holder" now they call me "hot"."

Earlier today she tweeted a picture of herself in more typical get up, sporting bright blue hair and a dress complete with what appeared to be either riding whips or windscreen wipers. Read Katy whips up a new look.