Here is the title and a synopsis of the episode.
3. GIVE AND TAKE
After an altercation with a deranged droid Lister has his kidneys organ-napped. The only solution is to ask Cat, the most selfish creature in the universe, to give him one of his.
Lister with one of Cat's Kidneys?
Could work!
OK, if Lister never had his kidneys when the droid tried to take them, whose kidneys were in the jar???
Would that even be possible. Humans and cats are two different species.
Heck, kidney transplants between humans is iffy, unless the right donor is found.