Hayley Summers was one of Dave Lister's ex-girlfriends.
Dave met Hayley when he was in his band, Smeg and the Heads. She worked in the bank where he had his account, which was always overdrawn. She started to date Lister and the two of them would spend saturdays in bed watching zero-G football and eating curry. She was the first person who had ever mentioned the expression "The real McCoy" to him and scrunched up her nose when she told him a story. He found it really cute.
Hayley took her job in the bank seriously, often telling Lister that she had to work a late shift. She was one of the only girls he ever really liked who didn't dump him. Instead she was offered a "dream job" on Callisto, which she couldn't turn down. He joined the Space Corps shortly afterwards.
3 million years later Lister received a letter from Hayley via a post pod. Rimmer snatched it away and read it. Hayley said that she had something important to tell him. Rimmer immediately thought that she was a transsexual, owing to her love of football and curry. He asked Lister if she shaved or if she had big feet.
She explained that she was 7 weeks pregnant and that she was unsure who the father was: Lister or her colleague Roy, who used the bank's finger-wetting machine a little too much for Lister's liking. The letter still smelt of her perfume. She told Lister that she was to have a DNA test to determine the parentage of the baby.
Lister realised that there must be a second letter in the pod that would tell him the result of the test. The Cat told him to put all thoughts of Hayley and Roy from his mind, forgetting all the nights when she claimed to be working late at the bank but was really with Roy. The more scenarios The Cat suggested, the less Lister could ignore them.
Lister convinced himself that if Hayley had been carrying his child, then he would have had descendents. This cheered him up as he thought she would have raised them well. He described her as "a wonderful woman" who would have raised his child to be a success. When he finally found the letter, he discovered the truth and refered to Hayley as "an absolute slag", miming the use of the finger-wetting machine. (RD: Dear Dave)
Behind the scenes
Hayley and Roy may have been named for Hayley and Roy Cropper, characters from Coronation Street. In that show, Hayley was a transsexual in the same way that Rimmer believed Lister's ex-girlfriend to be a a man.