7. Professor Lazarus - The Lazarus Experiment (2007)
Hot on the heels of the Pig Slaves came the Lazarus Creature in the following episode. The Lazarus Experiment saw elderly scientist Richard Lazarus (Mark Gatiss) alter his DNA to reverse his age, only to trigger a latent and long rejected form that humanity once had. Which apparently is a weird scorpion thing that looks like it was lifted from a video game cutscene. As Lazarus himself, Gatiss does an excellent job but when the episode breaks out the poorly rendered scorpion monster, it just looks and feels incredibly silly. Particularly with Lazarus flip flopping from being a well-read intellectual to a snarling monster at the drop of a hat at various points throughout the episode, even though his intelligence remains the same. The whole thing smacks too much of a 1950s B-movie without it being done in a way that ties it into more modern sci-fi and it feels a bit dated as a result. It wasn't so much a bad concept (broadly speaking) in itself as much as it was brought to the screen badly. In both the specific idea for the monster and the poor CGI.