Donkey Kong Junior 
First Appearance:
Donkey Kong Junior (Arcade, 1982)
Latest Appearance:
Super Mario Bros. 3: Super Mario Advance 4 (GBA, 2003)
Nintendo's own Son of Kong is a curiosity in that he was one of Nintendo's very first superstar characters, yet he has spent his twenty-nine years of existence in the shadows, taking only minor and infrequent roles. He burst onto the scene in his own action arcade game, then virtually disappeared; after a couple of Game & Watch titles and his own NES "edutainment" game, he was ushered into obscurity for years.
Junior returned to join the roster of playable characters in 1992's
Super Mario Kart, then went on to play a role in 1994's
Donkey Kong for the Game Boy. The character did not benefit from the DK renaissance brought about by
Donkey Kong Country, however, and thusly never achieved the same new-age prominence as characters like Diddy Kong, Dixie Kong, and Funky Kong.
Junior was a playable character in
Mario's Tennis for Virtual Boy and the similarly-titled
Mario Tennis for N64. He was also a fixture of all four installments of the Game & Watch Gallery series. Since then, however, Junior seems to have passed back into the familiar realm of obscurity which he has always inhabited, biding his time until Nintendo decides once again to dust him off and let him out to play.
Until next week, I leave you with this palate-cleanser: