Holly's user interface appears on ship screens as a disembodied human head on a black background, and can also be downloaded into a watch worn by Lister, Kryten's chest display, and on a motorcycle speedometer when the crew visited Waxworld.

In 'Skipper', the final episode of Series XII, Holly re-appears in a brief appearance when Rimmer travels to a point in time where the crew are about to be killed by the radiation leak as demonstrated in The End.

He often plays practical jokes on the crew, such as fooling Lister into thinking that NORWEB Federation space fighters were after him and wanted £180 billion in arrears for leaving his bathroom light on three million years ago, as well as wanting to arrest him for "Crimes against Humanity" as he had left some mouldy German sausages alone in his apartment for three million years and now the mould covered 7/8 of the Earth's surface.

Among his achievements was the invention of Hol Rock,[4] where he decimalised music (having ten notes instead of eight—although he admits that this would result in "piano keyboards being the width of a zebra crossing, and women being banned from playing the cello"), writing an A-Z guide to the universe and reading every book in existence (concluding that the worst was Football: It's a Funny Old Game by Kevin Keegan).

He was found on a planet made of junk from Red Dwarf, having reverted to his original male form, and was downloaded into Lister's Holly-watch.

The non-senile version only appeared in one episode, Back in the Red, Part III, and was distinguished by having an enormous forehead shaped like an egg.

The original Holly then states that he was responsible for re-engineering the Nanobots to resurrect the dead crew, all for the purposes of distracting Lister from going insane.

Kryten briefly mentions Holly in the series X episode Fathers and Suns, saying that the crew "miss" him before installing Pree, another computer.

This version of Holly was still senile but located in an alternate universe which Rimmer enters, set just before the crew are wiped out by the radiation leak.

Temporarily retreating to Starbug, the crew are eventually able to trick the new Holly into downloading the experiences of the original from the Red Dwarf archives, which restores his senility but also his old personality, prompting him to help them reclaim the ship from the rogue Cats.