The ITV presenter, 36, could barely contain her excitement at the beginning of the show when she and her co-host Phillip Schofield, 55, revealed that they would be dressing up later in the programme.
The duo left This Morning in the hands of Rylan Clark-Neal, 29, and Alison Hammond, 42, while they went to get ready for the big reveal.
Not to be left out, Rylan looked spectacular in a Maleficent costume complete with horns, whilst Alison took on the role of Ursula from The Little Mermaid.
Holly Willoughby finally put an end to the suspense when she paraded into the studio dressed as a magical unicorn.
“This is the best day of my life,” she giggled as she showed off her ensemble.
With a flowing rainbow mane and tail, a skintight white top and draping furry fabric to create the hindquarters of the mythical creature, Holly added a touch of sex appeal with a white corset which cinched in her slender waist.
This Morning viewers flooded to Twitter to gush over her outfit, with one praising: “@hollywills looks absolutely beautiful as ever as a unicorn.”
“Holly looks fab,” another exclaimed, while a third chipped in: “So jealous of @hollywills unicorn outfit, I wanna be a rainbow unicorn.”