Darth Vader (Survival)

Returned to her old haunts in Perivale in 1989, Ace learned from Ange that their mutual friend Flo married a "brain-dead plumber" whom they had nicknamed "Darth Vader". (TV: Survival)

Behind the scenes
Although not mentioned in the DWU, 'Darth Vader' is the name of the main antagonist of the Star Wars original trilogy. It is very likely that Ace and Ange nicknamed the plumber this as a reference to the Star Wars antagonist of the same name.