The Rejuvenation Shower is a technology aboard Red Dwarf discovered by Kryten and used by the Boys from the Dwarf. In theory, it was used to restore youth in a human by using a form of time travel to restore their physical body to an earlier state. If installed incorrectly, it could be used for time travel; however this only occurred erratically and this form of time travel was unstable.
With a flat-pack type assembly, the instructions read: "With just an Allen key and a Phillips-head screwdriver, assembly should take no more than three hours. Please consult diagrams 1 through 369 for further instructions. Do not forget to install the alignment bracket."
Kryten collects the Dwarfers in the sleeping quarters and presents his find: a rejuvenation shower, which is capable of rewinding in time any living being's genome back to its physical prime. The crew are intrigued, until Arnold Rimmer points out that it is a Swedish-made flat-pack self assembly and they have to build it themselves.
In a bungle of parts and effort, the crew get to work. Dave Lister eventually proclaims it to be done after complaining that they had taken it apart and rebuilt it "over a hundred times", despite Cat's insistence that there are too may spare parts still lying around. Deciding that they should test it on something unimportant first, they place one of Lister's more infested socks into the shower. Once the machine is activated however the beam extends farther outward than it should due to a lack of alignment brackets.
The crew find themselves encased in "beamer light" and are teleported away from Red Dwarf to a distant forest. Kryten checks his internal chronometer and finds that they have reached the land of Albion (or Britain) back on Earth in the year 23 AD. Since the Returner Remote which could undo the effects of the time warp has no batteries, the Dwarfers are stranded there. They decide to make a battery out of lemons - however the nearest lemons are in India, 4000 miles away. The Dwarfers then begin an epic cross-continent journey to locate some of the fruit. ("Lemons", Series X)
- Since Dave Lister was a native of England and had spent most of his youth there, this may explain why the Rejuve Shower transported the Dwarfers back to England. They were only a little over 2000 years out from Lister's youth, which was not wholly inaccurate considering the Rejuve Shower had transported them three million years into the past, and was not meant for time travel in the first place.