Singer/actress Taylor Swift channelled her feelings from a "traumatic" childhood arts and crafts session to play a nerd in a comedy sketch on America's The Tonight Show Starring Jimmy Fallon.

The I Knew You Were Trouble hitmaker reveals she loved making castles out of Popsicle sticks when she was a kid, but one arts and crafts session with hot glue went awry, leaving her bloodied and in pain, and she now has a scar on her right thigh as a daily reminder of the bad experience.

She drew on her arts obsession during her U.S. Tv appearance on Wednesday (13Aug14), when she portrayed a geeky character named Natalie to take part in Fallon's popular skit Ew!, in which the talk show host dresses up as a teenage girl, named Sara.

Discussing the sketch, in which Swift donned fake braces and oversized reading glasses, she explained, "The whole, 'I'm Natalie, I like to create Popsicle stick castles by myself sometimes' - that's actually a story from my own childhood.

"I have this scar on my leg and it's a very prominent scar that I've had ever since I was about 10 or 11 and everybody always asks me about it... I end up telling them. And at first I would tell people it's a normal thing, when I was 10 I would sit up in my attic and make castles out of Popsicle sticks and use a super industrial-strength hot glue gun 'cause I was really serious about it.

"So one day I was really aggressively creating a slide... and I was just like, glue, glue, glue, glue, glue, glue, glue, and then suddenly I was gluing off the table and a blob of just, like, hot glue, was just there (on my thigh). Your first instinct is just to go, 'Oh, I'll pull that off', and then you pull off 17 layers of skin with it... Ew! So that's how I came up with Natalie, it was a traumatic childhood story."

And Swift admitted she had been waiting for the opportunity to bring Natalie to life for some time: "I don't know why I got so into this but I love the Ew! sketch... So I started thinking, 'What would I ever do if I ever got to do that?'"

Fallon has previously recruited show guests including Zac Effron, Channing Tatum and Seth Rogen to don drag for the segment, while Lindsay Lohan and U.S. First Lady Michelle Obama have also appeared in the skit.