-Arnold Rimmer ("Thanks for the Memory")
As Dave Lister and Arnold Rimmer once argued about the nature of love, Rimmer said that he didn't believe in love, and that he was a member of the Love Celibacy Society because he thought love was a sickness that holds back your career and makes you want to spend all your money. Lister retorted that he only said that because he could never get a date. Rimmer replied to Lister that he had been on a date - with Yvonne McGruder. Lister reminded Rimmer that McGruder had been hit on the head with a winch and had a concussion at the time, believing Rimmer to be somebody named "Norman" when she went to bed with him. Rimmer said that it was her fault for being concussed. ("Confidence and Paranoia", Series I)
Later, Rimmer would drunkenly admit to Lister after his deathday party that McGruder had been his only sexual liaison. This event took place 16 March of an unstated year from 7:31 p.m. to 7:43 p.m., counting the time it took to eat the pizza afterward. Rimmer sadly said that he had spent more time in his life being sick. Before going to bed and passing out, Rimmer said that he would trade in his pips, long-service medals, swimming certificates, telescope, and shoe trees to be loved and to have been loved. Feeling sorry for Rimmer, Lister decided to go down to the Hologram Simulation Suite where he pasted eight months of his own memory into Rimmer's, giving Rimmer one of his old girlfriends. Lise Yates. Lister's "present" had consequences that he did not intend, however. ("Thanks for the Memory", Series II)
Better Than Life Appearance
McGruder appeared in Rimmer's Better Than Life simulated reality (this remains the only time that McGruder has actually appeared in the television series). She first materialised in the passenger seat of his car, a Jaguar E-Type, appearing attractive and acting seductively. They had sex, since in the T.I.V., Rimmer could touch things. However, as Rimmer's neuroses began to destroy his fantasy, McGruder appeared the next day pregnant and surrounded by a horde of unruly children virtually sired by Rimmer. ("Better Than Life", Series II)
McGruder was later mentioned by Lister in the Series VIII episode "Back in the Red, Part One" in Lister's and Rimmer's cell in The Tank, saying he'd previously had a relationship with her before she went out with Rimmer. In a (very successful) attempt to infuriate Rimmer into speaking, he described his sex life with her in great detail, including a mention of carpet burns. Whether Lister actually went out with her is never clarified, since he was trying to aggravate Rimmer, although it is also quite possible considering the great number of sexual relationships Lister has had.
In the deleted scenes of the Series VIII episode "Pete I", McGruder was also resurrected by the nanobots (although she remains unseen) and has entered into a relationship with Officer Denton. Finding Denton frozen in time by the Time Wand, a jealous Rimmer takes the time to play a prank on the frozen Denton.
In the Doug Naylor novel Last Human, which takes place in an alternate universe to the television series, McGruder has ended her relationship with Rimmer without much note. Upset by Lister taunting Rimmer that she only slept with him - in an elevator no less - due to a concussion, he decided to wait for her to call him back instead of seeing her himself. Yvonne had a crush on Rimmer and thought the liaison was all in her head due to the concussion and hoped that he would call her and prove it was all real. When the call never came, the affair ended before it even began and all that persisted was the odd smile whenever the two passed in a ship corridor. She survived the Cadmium II by not being on board the ship at the time, pregnant with Rimmer's child.
Based on the need for a strong father figure for the young boy, Michael McGruder, Yvonne regaled him with fictitious stories of bravery and triumph as Rimmer rose to greatness in the Space Corps. These stories did indeed lead the boy to a successful military career which led him to be selected for a mission on Mayflower to create a new home for humanity in the face of the then doomed Earth. Learning about the holographic reincarnation of his father from the recovered Red Dwarf black box, his ambition was to meet his father, a person he still felt less successful than. When he did meet his father, his illusions were shattered. Things were changed in the end as Rimmer won his son's respect by sacrificing himself to save Michael and others from the Rage.
When Rimmer breaks the news that what Yvonne had told him was a lie, he stressed her parenting abilities and stated that he was amazed at how good a job she had done in raising his child. He also expressed a twinge of regret that he had not also survived, given that she would have likely called upon him again.