Crew or equipment visible: Just after Blackadder waves to his dinner guests and enters the time machine for the first time, you can see a blonde crew member wearing a red shirt pushing up the end of the drawbridge-like door to close it as Baldrick is climbing up through the trap door inside.
Anachronisms: When Blackadder runs into Shakespeare after his visit with Elizabeth I, he picks up a copy of "Macbeth". "Macbeth" was written during the time of James I.
Anachronisms: When Blackadder exits the time machine in the Elizabethan era, the lights in the basement are electric wall lights and couldn't have featured in an Elizabethan building.
Audio/visual unsynchronized: When Blackadder walks down the stairs showing Leonardo Da Vinci's sketchbook, we hear him talking about it, but his lips don't move.