A Hologram Projection Cage, also called a Hologramatic Projection Cage or simply a Hologram Cage, was a hologram-related equipment that could be used to generate holograms outside of their normal field of projection, and exist outside of their spacecraft of origin, for extended periods of time.
However, when the gang passed by a suitable planet, they descended down to the surface in a Blue Midget to have a party and celebrate Rimmer's deathday. Rimmer was able to attend since they also took down the Hologram Projection Cage, along with the Holly Robot and two skutters.
Although Rimmer was constricted to the confines of the cage whilst on the surface of the planet, the cage was able to simulate extreme drunkenness for Rimmer, like the others. Rimmer didn't believe that he was drunk, but still felt the effects generated in the cage when back aboard Red Dwarf hours later. This enduring intoxication led to Rimmer telling Lister about his one-and-only lover, Yvonne McGruder. Feeling sorry for Rimmer, Lister decided to give him a very unusual deathday present. ("Thanks for the Memory", Series II)
- In later episodes, Rimmer was able to move around outside Red Dwarf without the use of the Hologram Projection Cage. For example, in the Series III episode "Timeslides", Rimmer was able to go back in time to Io House to talk to his younger self. This increased hologram mobility would later be explained in the Series IV episode "Meltdown" as being a result of Rimmer taking to using or learning how to use a Light Bee. The Light Bee was much less cumbersome and much more efficient than the cage, essentially a miniature Hologram Simulation Suite buzzing around inside him to project his image, negating the need for the cage in later episodes.