When a segment on the Sonic Screwdriver mentions that it first appeared in Fury from the Deep, an audio recording from its first use in that serial is heard, but the video clip that accompanies it comes from a later serial with Patrick Troughton as the Doctor. This is because no episodes of Fury From the Deep exist - only audio recordings, still photographs and some clips remain, and it is the chronologically latest story that has all of its episodes missing.