"Wait a minute - I don't see how you can have two sons without a woman on this ship."
"I dunno, but it will be a laugh finding out."
How many times had he thought about that weird, mysterious pair of images, the photo of himself, exhausted and not looking any older than he had been at the time, holding two small babies, and then being urged to run to the Medical Unit by that ancient version of himself?
Dave Lister was not a scientist; back when he was a kid, and then later a teenager, he had just tuned out the teachers, preferring to bum around, bunk off, or failing that draw little beards on the sperms in the biology books, but he was far from stupid.
He had after all come up with a plan to get away from the JMC after becoming so fed up with it all. The only downside was Rimmer smegged up by messing up the repairs to the drive plate, unleashing a blast of radiation that wiped out the whole crew, forcing Holly to take the ship into deep space and wait until the radiation faded.
The downside was the radiation would not die down, not for 3 million years. Only afterwards did he come out of stasis after his plan to just get away from Red Dwarf after his relationship with Kristine had fallen through, and he had decided to reveal Frankensteins' existence by having that incriminating photo of himself developed in the labs because he had become so heartily sick and tired of Red Dwarf, the JMC, Rimmer and his pointless attempts to become an officer, and the boring day to day crap as a technician on a ship that passed through the solar system, and he had encountered those Future Echoes after the Dwarf broke the Light Barrier, Lister had learnt a fair bit about those nasty time paradoxes.
Many people tended to underestimate David Lister, believing him to be nothing more than a washed-out, curry and lager-obsessed piece of scum, but he wasn't. The Future Echoes had made him realise if they had encountered one weird thing, weirder than meeting an evolved cat from the animal he had loved, they would meet more, and he had decided to brush up on what they could find.
That image of himself shaving himself before cutting himself on the chin whereas a moment before he had been shaving somewhere else before screaming for Rimmer.
That encounter with Rimmer in the Drive room where he spoke weird, only to discover a few moments later he was saying one thing to his deceased bunkmate and Rimmer was merely trying to tell him something he had heard before.
The Cat broke his tooth, only to discover it would happen later in a scuffle.
Rimmer saw a version of someone whom he thought was Lister being blown to bits.
Meeting an old version of himself on the bunk, locks reaching the floor, with an artificial hand with a designed bottle opener, telling him and Rimmer about Bexley being the one Rimmer saw die, and telling him to run to the medical unit.
Those Future Echoes were relatively logical and made some degree of sense, and they unfolded reasonably quickly, although looking at his older self made Dave wonder what happened in the in-between years; whether Red Dwarf returned to Earth and if the human race survived or not, but his future self had been more focused on something a little simpler.
But what didn't make sense, and over the last year, where Lister, Rimmer, and the Cat met Kryten, went back in time using the stasis leak where he learnt there was a chance he and Kochanski could make it work, and when Holly pretended to be Queeg, Lister had occasionally wondered about the last Echo, the one that made little sense, and the events behind it hadn't unfolded like many of the other Future Echoes they'd seen so far, and he had wondered how it even happened.
The echo when he stepped out of the medical unit, carrying two small crying baby boys.
Where had they come from?
Who was the mother?
Why hadn't he seen any sign of another parent?
How could he have two boys without a woman on Red Dwarf? Lister was the only member of the original Red Dwarf crew to survive the accident which wiped the whole crew out. He had done that by going into stasis, which was one of the motivations behind using the stasis leak, to go back in time and save Kristine before she died, while Rimmer merely cared for himself and wanted to save himself, not realising that the original Rimmer needed to make the disaster happen in the first place, and had the hologram stupidly forgotten the mess he caused when he'd swapped Kochanski's holo disc with his spare disc, and they had eventually become unbearable?
And then Lister got the answer. It had completely slipped Lister's mind when they'd crossed over into a parallel universe, which was largely identical to their own, except their counterparts were female, and had identical lives except for that difference (except Cat, since his double had been a male dog, which hinted that Deb Lister's plan involved dogs rather than cats) that he was about to discover where those boys came from.
He and Deb Lister had slept together and had sex, and now Lister discovered he was pregnant, because of the different laws in the other universe.
Lister had thought his mind was going to shatter. He couldn't believe it; he had assumed that Red Dwarf would fly into a time warp, or another opportunity with the stasis leak would be the reason why he had two boys, having them by carrying them because of a night with a female version of himself was the last thing he'd expected.
When the pregnancy test (all 26 of them) had confirmed he was in fact pregnant, Lister had retreated to the library, hoping to learn more about pregnancy so he could prepare for this. To Rimmer and the Cat, this was a joke, but after going through the books, learning what was expected, what he'd need to do to prepare for the babies beyond the basics he had picked up on over the years, Lister was sure he was not laughing any more.