Taylor, 24, looked unrecognisable as she transformed into nerdy 13-year-old Natalie Benson for the Ew! sketch on Wednesday (13 August).
Embracing her role as Natalie, Taylor donned a striped button shirt, red glasses and lots of hair scrunchies!
In the sketch, Taylor joins Jimmy - aka Sarah - on the sofa and lists her interests, which includes having a band aid collection.
The pair then showed off their dance moves as they paraded around the living room to Selena Gomez's catchy single, 'Come & Get It'.
However, the funniest part was when Taylor took part in the quick-fire 'Ew! speed round' where Taylor made the hilarious revelation that she'll "never, ever, ever, ever" get back with an ex!
'We Are Never Ever Getting Back Together' singer Taylor went through a pack of cards - such as rice pudding, airplane modes on mobiles and breaking up with an ex - which all ended up in the 'ew' pile.
When it came to the card asking if she would get back with an ex, Taylor said 'ew' once more.
"Never?" Jimmy continued to ask.
"Never, ever, ever, ever, ever!", replied Taylor, leaving the studio audience in hysterics.
Over on the main show, Taylor, who looked glamorous in a rose-printed mini dress, confirmed that she will be performing at the MTV Video Music Awards on 24 August.
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Watch Taylor and Jimmy in Ew! below: