10 Doctor Who Scenes You Didn't Realise Were Tricking You

Speaking of The Eleventh Hour, Prisoner Zero was a memorable first villain for the Eleventh Doctor for a number of reasons.

For one thing, he was completely absent from promotional material in the run-up to Series 5, which meant that his inclusion was a fun surprise. And for another, his various forms were brought to life by an impressive array of guest actors: voice of Pingu Marcello Magni, award-winning actress and general icon Olivia Colman, and, of course, Matt Smith.

But like most things involving CGI, he also caused something of a headache for the production team.

As showrunner Steven Moffat recalled during the Doctor Who Lockdown! Eleventh Hour tweetalong, superimposing Prisoner Zero’s teeth into Magni's mouth was easier said than done.

“God, we couldn’t get the fangs to track at all,” he remarked. “It looked terrible.”

There wasn’t enough time, or money, to fix the fangs completely, but Moffat and fellow executive producer Piers Wenger were, at least, able to make the issue less noticeable. The day before the press launch, they went in and added camera shake to these shots, which does a pretty good job of masking the problem.

Thankfully, Olivia Colman’s gnashers were on much better behaviour.