Bowser is a huge, burly, green-shelled Koopa with spikes, horns, and hair. His bushy eyebrows and mane are fittingly a bright, fiery red-orange and has bright red eyes. He sports two small horns, many spikes on his shell (similar to a Spiny) with brown-orange spike-rings, as well as along his tail (minus the spike-rings). He wears several spiked collars around his neck and arms. He has three claws on each of his massive feet, which support his impressive girth. He has three claw-tipped fingers and a thumb on each hand, and his arms are noticeably burly, indicating his vast physical strength. While his face and his shell are green, his underbelly and snout are flesh-colored (occasionally depicted as being closer to tan or even yellow), and his tail and limbs are an orange-tinged yellow. The exact coloration of Bowser's head varies depending on the media: while official 2D artwork and most of his in-game appearances have his head and shell match in color, the majority of the official 3D artwork, trailers, merchandise as well as Mario & Luigi games show him with a light green head, similar to Bowser Jr.'s appearance.
Bowser's appearance is based upon a combination of the many species of Koopa, including Koopa Troopas, Spinies, and Hammer Bros. According to Prima's Super Mario Galaxy guide, the appearance of Bowser and the Koopas are also based on kappa of Japanese mythology, although this has not been officially stated by Shigeru Miyamoto.
Bowser's appearance is not always the same. Graphical limitations in the original Super Mario Bros. meant Bowser could not have hair; artwork for Super Mario Bros: The Lost Levels depicted him with yellow hair, and his iconic red hair was finally seen in-game in Super Mario Bros. 3. The original Super Mario Bros. also depicted Bowser as being mostly green, rather than having yellow body scales. The creators of the Mario cartoons wished to follow the graphic design of Super Mario Bros., and so their portrayal of King Koopa had him almost completely green in colour and lacking hair, with a crown atop his head instead. His stomach was a deeper yellow than in later game depictions, and the whites of his eyes were also yellow; he also had a more crocodile-like snout, which was also colored green. He was also given a single pair of spiked bands on his wrists, with the spikes on said bands being yellow in color.
Nintendo Comics System used the same design as the cartoons for the Mario comics, and different installations in the Nintendo Adventure Books used either it or Bowser's game depiction, interchangeably. By comparison, the two Mario anime (the three OVAs and Super Mario Bros.: Peach-hime Kyushutsu Dai Sakusen!) are relatively true to the games' depiction of Bowser, except for the fact that his eyes are blue instead of red.
- As told in Prima's official Super Mario Galaxy guide.