King Dedede (name pronounced dee-dee-dee), known in Japan as Dedede Daiō (デデデ大王, Dedede Daiō, lit. "Great King Dedede") is a major recurring antagonist (and anti-hero) from the Kirby series.
 Character Description
King Dedede is the selfish, self-proclaimed king of Dream Land. He has appeared as Kirby’s rival and nemesis in many Kirby games since Kirby's Dream Land. He is a hammer-wielding penguin with fine robes and a greedy disposition. His powers are vaguely similar to Kirby's; he is able to puff himself up and float (although he only got this ability through rigorous training after his first defeat at Kirby's hands), and suck up enemies and spit them out as high-speed projectiles (unlike Kirby, he cannot copy a foe's ability). While his more heinous actions are influenced by being possessed by Dark Matter, he is usually considered to be the main villain of the Kirby series.
However, a common misconception about King Dedede is that he is an "evil" character. He seems to be more selfish than evil, and appears to otherwise have a good heart. King Dedede's actions range from stealing food from the Dream Land residents in Kirby's Dream Land to breaking the Star Rod, source of power in the Fountain of Dreams, into seven pieces in Kirby's Adventure (although this latter was to protect Dream Land from an evil it did not know about). However, he is not above teaming up with Kirby as a friendly rival on occasion, such as in Kirby 64: The Crystal Shards, or Kirby: Canvas Curse. King Dedede's relationship with Kirby is more along the lines of friendly competition, begrudging admiration, and annoyance on both sides than flat-out hatred or villainy. King Dedede also appears helping Kirby as a playable character in Kirby's Return to Dream Land.
In Brawl, he is voiced by Super Smash Bros. and Kirby series creator, Masahiro Sakurai, who also voiced Dedede in Kirby 64: The Crystal Shards.
 In Super Smash Bros.
In the original Super Smash Bros., King Dedede made a mere brief cameo in the background of the Dream Land stage.
According to a page on the Japanese Super Smash Bros. site, King Dedede was planned to be playable, but was cut; Bowser and Mewtwo are also mentioned as having been cut, though no other information is available. 
King Dedede only reappeared in the Dream Land stage once again, and also making another appearance as a trophy. Once again, King Dedede was planned to be a playable character in Melee, but wasn't included in the game due to time constraints.
 As a trophy
King Dedede makes an appearance as one of the 100+ collectible trophies in the game that can be found by "typical" means - either through the Trophy Lottery or picking it up during one of the single-player Regular Matches.
 Trophy Description
King Dedede is a playable character in Super Smash Bros. Brawl, making him the third playable character from the Kirby series. He wields his trademark hammer, swinging it in most of his standard attacks, like the Ice Climbers, and has very powerful hammer-based attacks. His special moves are Inhale (neutral special), Waddle Dee Toss (side special), Super Dedede Jump (up special), and Jet Hammer (down special). Inhale is very similar to Kirby's trademark move, but King Dedede lacks the ability to copy abilities. Waddle Dee Toss lets the king throw his minions at foes, sometimes producing not only Waddle Dees but also more deadly Waddle Doos and Gordos. It is also possible for Dedede to throw out capsules containing items. Super Dedede Jump is an effective recovery move, sending King Dedede high into the air, then crashing into the ground to damage foes. He can also cancel out of doing this. Finally, King Dedede mechanizes his hammer with Jet Hammer. The hammer's power is charged up by holding the special attack button, and then released for a mighty swing. King Dedede incurs damage after charging for too long, however. His "trip" attack and Super Dedede Jump come from Kirby's Adventure.
Like other playable characters, King Dedede appears visually similar to his canon incarnations, but greatly enhanced graphically - for example, his usually uncovered girth (other than his patterned waistband, that is) is now covered by fine robes of a similar color, making his overall wear resemble a kimono. He also has several interesting costume colors, which not only change the color, but the design on his waistband too.
King Dedede currently ranks 12th on the tier list in C+ tier.
 Trophy Info
The self-styled king of the amazingly peaceful Dream Land. He continually does things unbecoming a king, like stealing the kingdom's food supplies or all the stars from the sky. He's not all bad, though, and sometimes performs good deeds. While he and Kirby often battle,they've been known to compete good-natured at speed-eating contests and minigames.