David "Spanners" Lister is Ace Rimmer's friend and engineer from another dimension than our own. He is married to that reality's Kristine Kochanski with two children, Jim and Bexley. He appears in the episode "Dimension Jump" and the novel Backwards.
Spanners was a flight engineer in the Space Corps and helped to build Ace's Lightship. He was physically identical to the primary Dave Lister, except that Spanners wore glasses and had a moustache. He was pleased when Ace refused to attend the banquet to honour the pilot's achievements, choosing instead to join the engineers in the mess.
His role was heavily expanded upon in Backwards, with Spanners being portrayed as a hard working if still sometimes slobbish flight engineer who was known for his strong work ethic and dim view of authority. For instance, it is shown that he had a habit of working long into the night until the early hours of the morning, although by the time of the events of the novels both his slobbiness and work ethic were being diluted by his happy domestic life with his wife Kristine Kochanski.
He was a good friend of Ace's and is also friends with Olaf Petersen, who he knew from his days serving on his reality's version of Red Dwarf. In his reality, Spanner's bunk-mate was not Rimmer but Lewis Pemberton, who encouraged Lister's own development, helping him reconcile with Kochanski and starting him on the classes that led to him becoming the engineer he is when Ace meets him. As Ace departs, he leaves Spanners with the keys to his holiday villa so that Spanners can go away for a time with Kochanski and his children.
When Ace entered the prime universe and met the Red Dwarf crew, he struck up a friendship with the fifteen year old Lister (who had spend nearly half a century in the backwards universe). When learning of how well his counterpart did for a living, Lister was pleased for him, glad that there was a version of himself living a great life, a stark contrast to Arnold Rimmer's attitude towards Ace.
Behind the scenes
Craig Charles thought that when he was made up as Spanners, he looked like his uncle Hugo.