Don't mess! Casual Megan Fox brandishes her knuckle duster iPhone case on the set of Teenage Mutant Ninja Turtles

You’d best not mess with Megan Fox.

The 27-year-old actress is currently shooting scenes for forthcoming film Teenage Mutant Ninja Turtles in New York, where she was spotted relaxing between takes on Thursday.

Megan looked casual in a plaid lumberjack shirt and light blue joggers as she stepped out of her trailer, her long raven hair naturally parted down the centre and flowing loosely across her shoulders.

The actress also sported a pair of red flip-flops, while her minimal make-up – a hint of blusher and subtle lipstick – perfectly reflected the low-key look.

Megan Fox shows off her distinctive iPhone case on the New York set of Teenage Mutant Ninja Turtles

Fist sandwich: Megan Fox shows off her distinctive iPhone case on the New York set of Teenage Mutant Ninja Turtles

Megan's iPhone case catches the eye as she leaves her trailer

Attention grabbing: Megan's iPhone case catches the eye as she leaves her trailer

While the LA based star has always been easy on the eye, it was her distinctive iPhone case that really claimed the lion’s share of attention from photographers

Indeed, the faux-brass cover appeared to serve a dual purpose as a protective case and protection from any would be attackers.

The plastic case, available from US boutique Elizabeth Charles, matches the one used by actress Cameron Diaz on the New York set of latest movie The Other Woman in May.

Megan Fox dresses down between takes on the set of the new movie in plaid shirt and blue jogging bottoms
Megan Fox dresses down between takes on the set of the new movie in plaid shirt and blue jogging bottoms

Casual: Megan Fox dresses down between takes on the set of the new movie in plaid shirt and blue jogging bottoms

Other stars to favour the distinctive iPhone accessory include Rihanna, who was sighted with it earlier this year.

The cover – fashioned to resemble knuckle dusters – also courted controversy back in April when TMZ reported that former porn star Jenna Jameson had been arrested for attacking her boyfriend with it.

Megan - married to actor Brian Green, with whom she has young son Noah - will play April O’Neill in Teenage Mutant Ninja Turtles, a remake of the 1990 film that was based on the popular cartoon series of the time.

The new film will also star Whoopi Goldberg, Mos Def and Jeremy Howard.

Cameron Diaz sports the same iPhone cover on the set of her new film in New York earlier this year

Don't mess: Cameron Diaz sports the same iPhone cover on the set of her new film in New York earlier this year

Cameron's iPhone case could come in handy against potential attackers

Dual purpose: Cameron's iPhone case could come in handy against potential attackers

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