Dark Pichu is a manifestation of Pichu's inner darkness and a major antagonist in Season 13 due to orchastrating Pichu's descent into darkness, or rebirth, by convincing him that his friends have abandoned him. Dark Pichu later gains complete control over Pichu when Mewtwo attempts to exorcise him. During the finale, Dark Pichu puts his weaker half at stake during the Shadow Battle, but after getting damaged severly by Drago, Dark Pichu becomes the victim. He begs Pichu to spare him, but Pichu uses Thunderjolt to damage himself, seemingly killing Dark Pichu. However, Dark Pichu returns in Season 19 upon Professor Viper, Yami Marik, and Madara Uchiha's arrival in the Shadow Realm. In Season 20, Dark Pichu is given a synthetic body by Professor Viper, and is reborn. Dark Pichu later battles Pichu, but is unable to kill his light counterpart. When Pichu states they are one and the same, Dark Pichu realizes he was wrong to take advantage of Pichu, and reunites with his light counterpart. His current status is unknown. Though he is still fused with Pichu, Dark Pichu has not been seen since fusing with Pichu.
As he is a manifestation of Pichu's inner darkness, Dark Pichu looks exactly like Pichu. The difference is that Dark Pichu wears blue goggles and a blue scarf to symbolize his evil. During the finale, Dark Pichu's face would have the vains pop out. In Season 19, Dark Pichu has a tuft of hair sticking up to further distinguish him from Pichu.
Unlike Pichu, who is pure-hearted and kind, Dark Pichu is selfish and uncaring. He is also manipulative, as he convinced Pichu that his friends abandoned him. Dark Pichu is very sadistic, as he enjoyed seeing Jigglypuff perish. However, he valued his own life dearly, as he begged Pichu to spare him.
- Dark Pichu is the only antagonist that does not have a body, as he is Pichu's inner darkness. However, this was only during Season 13.
- Dark Pichu is similar to Yami Bakura in that they are master manipulators and survive by using another person's body. Unlike Yami Bakura, however, Dark Pichu had a change of heart.