A comical, non-canonical short story, "Who's Your Daddy," appearing in Star Wars Tales 20, presents Darth Vader practicing the way he plans to unveil his identity to his son during their destined lightsaber battle.
Darth Vader began his day like any other, performing his usual morning activities, such as brushing his teeth and eating breakfast. Throughout the morning, he continuously practiced how he would disclose the truth of Luke Skywalker's fatherhood to him. Eventually, he encountered Luke, but when the moment arrived to reveal the truth, he could only utter nonsense.