Here's a look at the filming of the classic Doctor Who story "Caves Of Androzani," where co-star Nicola Bryant is faced with a major acting challenge. She has to ad-lib saying "Doctor, what's happening?" and "Doctor, I'm frightened!" and making scared faces for, like, two minutes. Just in case they need a little extra reaction from Peri, the Doctor's traveling companion. This clip (which isn't on any DVD) shows just how tough it is to be a classic Who companion: you don't just need to be able to freak out, you need freaking endurance. Click through for another classic scared-companion ad-lib. This one comes from the filming of "Planet Of Evil," and is on that story's DVD. They're filming the cliffhanger at the end of episode one, when the anti-matter monster is advancing on the Doctor and Sarah Jane. Actor Elisabeth Sladen is screaming and hyperventilating her little heart out, and then she thinks the scene is over. But no. The director wants her to scream and hyperventilate a bit longer, just in case they need some extra material. Bear in mind both these scenes were probably recorded at 10 PM with the studio running overtime and everybody having been up since 5 AM and desperate to get to the pub. The other great bit from the "Caves" behind-the-scenes footage is director Graeme Harper telling Colin Baker that he has to sit up erect when he becomes the new Doctor, and then giggling for aqes about how funny it is that the Doctor is getting erect.