Dr. Wily
Doctor Albert W. Wily is Mega Man's main antagonist in the Mega Man series, and also Mario's enemy in the Club Nintendo comic "Super Mario: Verloren in der Zeit". He is a mad scientist planning to rule over Mario's city. In order to achieve this goal, he masquerades as a mailman and delivers Mario an Alarm Clock. Thinking that it is donated to him by a fan, Mario tries it out. It turns out, however, that in fact it is a time machine, taking him to various ages, past and future. In the meantime, Dr. Wily manipulates the citizens of the town, amongst others Yoshi and Mario's neighbour Miss Steinbrunnen. Wily even makes Princess Toadstool work for him. He has a fortress with an unknown location which Mario manages to enter. When detected by Toadstool, however, Dr. Wily ties him to a machine, seemingly in order to manipulate him as well. As it turns out, the story was only a nightmare of Mario's.
Though Dr. Wily never appeared in another Mario publication, he did appear in the TV show Captain N: The Game Master, occasionally alongside Donkey Kong. In this show, he was a technologically knowledgeable servant of Mother Brain.
Dr. Wily also appears as a trophy in Super Smash Bros. for Nintendo 3DS / Wii U.
Trophy information from Super Smash Bros. for Nintendo 3DS / Wii U
Blue indicates exclusive to the Wii U version.