The 'Once' singer told X magazine that she was so intimidated by the opening title sequence that it still prompts her to take a trip to the bathroom every time she hears it.
"[When I hear it], I need a poo," she said backstage at last week's results show. "Literally. Everything runs through me. 'Oh my God, I need the toilet right here right now'."
Speaking about her nerves during her stint on the ITV1 reality show, she said: "I'd never let myself break down in front of the cameras. I'd have the odd tear, but I'd wait, I'd compose myself, and I'd cry after.
"I'm a worrier, and every week I'd be sick before I went on stage, and I still do now, I get the runs - excuse me, but I do!"
Vickers finished fourth in the 2008 series of the television show, behind Eoghan Quigg, JLS and eventual winner Alexandra Burke.
> Diana Vickers: 'My Wicked Heart'