Pearl Mackie says Peter Capaldi told her 'Doctor Who' is a 'big, mad train'

April 3 (UPI) -- British actress Pearl Mackie says her Doctor Who co-star Peter Capaldi was tremendously supportive when she signed on to play his companion Bill just a short time ago.

Asked by UPI during a round-table interview with reporters at New York Comic Con if Capaldi is helping her navigate the sci-fi show and its legions of fans, Mackie replied: "When we filmed the trailer, he gave me two cards and a little candle as a welcome. He was like: 'This is all mad. It's a big, mad train, but just get on it and enjoy it as much as you can. And here's my number. If you need anything, give me a call. I know it can get a bit crazy, but, don't worry, you're not in this by yourself.'"

Although Doctor Who doesn't kick off its new season until later this month, Mackie said in October she was already getting loads of attention for the role.

"It's amazing. It's been incredible for me. I've not even done much TV before, so having something this high-profile and so well-loved, it's a lot of pressure, but it feels like being welcomed into a family. It's really nice," she confessed.

So, who exactly is her character Bill?

"She's not very scientific," Mackie revealed. "She's very smart, but it's not like she knows a lot about the world that she is going into, but she loves sci-fi."

The 29-year-old actress went on to say she likes how the time-travel show switches up its casting every few years, introducing new companions and re-inventing the Doctor by having different actors play him. Capaldi is the 12th actor to play the title role, but will be leaving at the end of this season, his third. His replacement has not yet been announced.

"It's kind of a chance to re-vitalize the series, not that it needed it, but I think whenever a new companion comes in, it's like a chance for the audience to see it again through their eyes," Mackie explained. "If there are new fans of the show, for example, because Bill is completely new to the whole world, it's like kind of starting again. So, they can come in without any prior knowledge of anything and she asks questions that maybe haven't been asked for ages, as well. Like, stuff about the Tardis -- she discovers its bigger on the inside than it is on the outside -- that kind of thing. The nice thing about her is that she asks those questions that you would expect, but she doesn't necessarily react in the way that you'd expect. So, it kind of gives you those iconic moments, but then it comes in with a fresh take, as well, which I think will be really interesting for the audience. I hope so anyway!"

The new season of Doctor Who will start on the BBC and BBC America on April 15.