During the bat attack scene at the end of the episode, as the Doctor and Romana are stopped in their tracks, one of the prop bats falls to the ground in front of them and lies still.
After the Doctor and Romana leave the village mess hall, Ivo produces a communication device and talks to someone. He uses the device like a walkie-talkie rather than a phone, but his lines suggest he is having a two-way conversation with someone - even though nobody else can be heard.