Kryten 2X4B - 523P is a Series 4000 service mechanoid currently stationed on the Jupiter Mining Vessel Red Dwarf. He was originally played by David Ross, but when Kryten became a permanent cast member, he was played by Robert Llewellyn. He lives to serve, and he is happy to do so, though he is incredibly neurotic.

Kryten was built by DivaDroid International in 2340, the Series 4000 models being caricatures of roboticist Professor Mamet's ex-fiance, the mechanoids' tendency of their head's blowing up over a build-up of negative emotion being an exaggerated quirk of said ex. Kryten was originally stationed on the SS Augustus, where he remained for decades. After the entire crew had died of old age, Kryten was alone until he was picked up by the crew of the Nova 5. He remained there happily for years, even after the ship crashed and the entire crew was killed. It has been hinted that Kryten was responsible for the crash by washing the navigation computer with soapy water. He refused to believe that the crew was dead and continued to fuss over their skeletal remains for centuries until his distress call was picked up by the crew of Red Dwarf. After talking some sense into Kryten, they took him back to the ship, where he began meticulously obeying every one of Arnold Rimmer's orders. Dave Lister tried instilling a sense of rebellion in Kryten, and it seemed fruitless until Kryten placidly began lashing out at Rimmer, took Lister's space bike and headed out for the stars to pursue his dream of growing his own garden.

Kryten crashed the bike into an asteroid however, and his remains were later found by Lister. Dave tried his best to rebuild the damaged mechanoid but mostly had to rebuild from scratch. His former personality was lost, and Lister later set about helping Kryten to break his programming, to little success. He has remained on Red Dwarf ever since, except for the period of time when he was on Starbug with the rest of the crew after Holly forgot where she had parked Red Dwarf.