The Bridesmaids actress has recorded a cover version of Bowie's classic 'Space Oddity' for her upcoming film The Secret Life of Walter Mitty.
However, she was later told by producers that her vocals would be overlaid by Bowie's original voice.
"I just found that out a couple of weeks ago - I guess they talked to him and it's now a duet on the soundtrack," Wiig told news.com.au. "It's so weird. I have to pinch myself."
She continued: "It was really fun recording that. I can't even describe it, just singing that song. It's David Bowie and I'm such a huge Bowie fan. It was intimidating. I've caught the bug now. I want to go on tour!"
Wiig stars opposite Ben Stiller in The Secret Life of Walter Mitty, which centres on a timid photographer who embarks on an adventure to recover a lost negative.
Sean Penn, Adam Scott and Shirley MacLaine co-star in the movie, based on the short story from James Thurber.
The Secret Life of Walter Mitty will open in cinemas this December. Watch a clip below: