Whereas rudimentary and routine science could be performed in the all-access Science Room, the more sophisticated laboratories of Z Deck acted as an area for advanced and classified research, for qualified scientists, unlike the regular characters.
Three million years later, the mechanoid Kryten explored Z Deck, retrieving the prototype Matter Paddle. Kryten used it to teleport to the others in the Officer's Quarters, and they then used it to teleport to the nearest habitable planetoid... ("Meltdown", Series IV)
When the rest of the crew were resurrected by the nanobots, the regular characters were sentenced to The Tank. Fellow prisoner Kill Crazy had a theory that the prison food was the cloning experiments from Z Deck that gone wrong. Kill Crazy got this idea when, in the prison canteen, Kill Crazy got a starter with "two noses" in it, and "it sneezed". Two other prisoners, Dave Lister and Jimbo Steel, were witness to this event. ("Pete: I", Series VIII)
Continually annoying Captain Hollister, Lister and Rimmer were sent on Punishment Detail, having to peel a mountain of potatoes. However, Lister had heard about the existence of a "programmable virus" in the Z Deck, and got Bob the Skutter to retrieve it for him. Intending it only eat the skins of the potatoes, it also ate Lister and Rimmer's clothes and hair. Hauled before the captain once again, naked and bald, Rimmer shook hands with the captain, giving him the virus too. As his clothes and hair disappeared, an enraged captain ordered them to two months in The Hole. ("Pete: I", Series VIII)
When the crew of Red Dwarf evacuated on the shuttles due to the Chameleonic Microbe, the regular characters were left aboard to die. Kryten was able to scavenge the now-empty ship for anything that may have helped them defeat the Chameleonic Microbe. Kryten was able to knock up a Prism Laser from parts he got from Z Deck, and completed the device in the Captain's quarters on Floor 341. (Only the Good... Series VIII)
When Rimmer mocked the Cat about his apparent virginity, Cat denied this, claiming that "Cats have two homes", and that he has two female felis sapiens lovers hidden away from the others aboard Red Dwarf on Z Deck. This is later actually seen, albeit in one of the Cat's dreams, and therefore seemingly remains a lie by the Cat. (Can of Worms, Series XI)