The continuity on Voyage was appalling.
Possible spoilers ahead!
I watched the third season episode "Day of Evil" today and was annoyed that (yet again) the writers had completely cast aside a previous episode that dealt with a similar theme. By that I mean Nelson and Crane coming face to face with themselves. Now in "The Sky is Falling", an alien craft landed in the ocean, and the occupant disguised itself as Crane and Nelson in order to interact with them. This is exactly what happened in "Day of Evil", yet neither Lee or Harriman could believe their eyes when they saw their doubles. Why did they not remember the previous encounter?
Take "Leviathan" as another example of this. When Riley said he had seen an underwater monster, Nelson (I think) said he must have been seeing things. Why was Riley not believed as the Seaview had already encountered quite a few monsters?
And don't get me started on "The Shape of Doom". It was more or less a carbon copy of "The Ghost of Moby Dick". Both episodes had an obsessed scientist tracking a sperm whale in the hopes of gaining information that could help humanity. "The Shape of Doom" also borrowed from "Jonah and the Whale" in that the former had the whale swallow a bomb, and in the latter it was the diving bell. Having three very similar sperm whale episodes in just a couple of seasons wasn't that original either.
I can understand that recycling footage helped to keep costs down, but I found it rather insulting when the writers didn't think that viewers would remember previous stories, and expected them to believe the characters had poor memories too.
Any more thoughts on this?