Gillan, who plays the Doctor's new companion Amy Pond, found herself "lying in a pool of sick with cabbage in it" for one scene, PA reports.
"That was quite bizarre," she said, adding that she has now learnt how to "act terrified of tennis balls".
She explained: "I've mastered that art for the CGI afterwards."
Gillan also claimed that her life has been "turned upside down" since she joined the show and revealed that she loves starring alongside Matt Smith.
"He's great to work with," she said. "You never know what's going to happen from one take to the next so I don't know what's coming."
> Gallery: 'Doctor Who - The Time Of Angels'