The princess and the pee! Sarah Michelle Gellar dazzles in a huge blue ball gown as she transforms into Cinderella in hilarious new snaps

PUBLISHED: 12:00, 28 January 2015 | UPDATED: 12:21, 28 January 2015

She looked as though butter wouldn't melt as she transformed into Cinderella for a new YouTube video.

But Sarah Michelle Gellar made sure to poke fun at her new alter-ego as she posted a series of hilarious snaps to her Twitter page.

Making it case of princess and the pee, the 37-year-old actress documented the rather un-ladylike act of using the bathroom in one of the comical images.

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The princess and the pee: Sarah Michelle Gellar documented the rather un-ladylike act of using the bathroom as she transformed into Cinderella in a series of hilarious Twitter snaps

Looking wide-eyed into the camera as a friend snapped away amid filming for YouTube series Princess Rap Battle, the former Buffy The Vampire Slayer actress hitched her huge blue ball gown up around her ankles as she used the toilet for all to see.

Alongside the funny snap, she wrote: ''Um......how did they do this???'

Wearing a glittering tiara nestled among her flowing bed of blonde curls as she posed alongside actress Whitney Avalon, the star wrote on her Twitter page: ''#LetTheRapBattleBegin!'

As well as her light-hearted take on life as a princess, Sarah had a few words to say about real-life beauty pageants, calling them 'cruelty to humans'.

Happy ever after: The actress posted pictures of herself on social media on Monday squaring up for an epic war of words in the popular YouTube series Princess Rap Battle

Ready to rumble: Sarah was taking part in the upcoming fourth Princess Rap Battle, the brainchild of actress Whitney Avalon (centre left), where two fictional princesses are pitted against each other

Acid tongue: Despite how much fun she had dressing up, Sarah tweeted, 'Can we finally end beauty pageants? Cruelty to humans? Let's never forget "The Iraq" #MissUniverse'

Sarah was taking part in the upcoming fourth Princess Rap Battle, the brainchild of Avalon, where two fictional princesses are pitted against each other.

The royal look obviously gave Sarah the confidence to speak her mind on social media.

She tweeted: 'On the subject of "Princesses", can we finally end beauty pageants? Cruelty to humans? Let's never forget "The Iraq" #MissUniverse.'

The actress was referring to Caitlin Upton, the Miss Teen South Carolina who went viral in 2007 after her excruciating answer at the Miss Teen USA pageant saw her reference 'The Iraq' when asked, 'Recent polls have shown a fifth of Americans can't locate the U.S. on a world map. Why do you think this is?'

Dressed down: On Tuesday, the actress had ditched the glamour for a trip to the gas station

It was a different story on Tuesday, however, when the busy mother-of-two ditched the glamour for a trip to the gas station in Brentwood, California.

Managing to stay under-the-radar, the Grudge star looked casual in a black cardigan, skinny jeans and studded Converse trainers while filling up her Prius - a popular car choice among environmentally-conscious LA celebs.

The Crazy Ones actress looked a world away from the red carpet with her hair quickly pulled into a messy half-up do and oversize sunglasses covering her face.

Something in your teeth? Sarah's diamond wedding band was on display as she pulled a funny face while getting to grips with the pump

Solo trip: The actress was without her husband of 12 years, Freddie Prinze Jr., as he recovered from major spinal surgery

Sarah looked like she was alone as she got to grips with the pump, which is no surprise as her husband Freddie Prinze Jr. has been out of action for several months following a major spine operation in November.

Her husband of 12 years tweeted on November 26 that he was 'learning to walk again', but Sarah rubbished the claims.

She told reporters at the 4th annual Santa's Secret Workshop in West Hollywood in December that, 'He did have very serious surgery, there's no question, but his learning how to walk again has been greatly exaggerated.'

Having been married for 12 years after meeting in 1997 on the set of I Know What You Did Last Summer, no doubt Sarah's used to putting her husband in his place when he gets prone to hyperbole.

The pair have two children together, five-year-old Charlotte and a two-year-old son called Rocky, neither of which appeared to be with Sarah at the gas station.