N64 Bowser's Castle

Bowser's Castle (transliterated to Koopa Castle on a few occasions ) is the last race course in the Star Cup of Mario Kart 64 and the last course in the Lightning Cup of Mario Kart Wii.

Mario Kart 64
It features several Thwomps that try to block drivers from getting to further areas. Near the beginning of the course, there is an imprisoned Thwomp tinted green with yellow teeth due to the lighting, which shakes and laughs if the player goes near it. The laugh can also be heard by the normal Thwomps throughout the course. The Thwomps' laugh is the same as Wario's, only pitched down. Because Wario's voice changed for the international release, the Thwomps' voices changed with it. In further corridors, there are pictures of Bowser and large stone statues that shoot flames from their mouths, but they are harmless. At the end of the track racers will race on the roof of the castle. On the last lap, or when the player gets too close to the Bowser statue at the start of the track, Bowser's laugh plays. Thwomps are the main obstacle in this course. Most of them will move around the room and try to crush the racers and some slide across the room. In the hallway where the pair of Thwomps chase down the player, the number of Thwomps at the end of the hall depends on the engine class (one Thwomp for 50cc, two for 100cc, and three for 150cc).

Mario Kart Wii
This course reappears as the last course of the Lightning Cup in Mario Kart Wii, and is the final course overall. The castle has been redesigned to become more realistic and windows have been added. In the final section, Lava Geysers spring out from the pits to cause the drivers to bowl over, especially when racers attempt to jump. Due to lighting improvements, the imprisoned Thwomp no longer appears green, but it still reacts when players drive near it. The evil laugh made by the sliding Thwomps in the original version is no longer heard; instead, they make angry expressions and rumbling noises. The flame-shooting statues are still harmless. Bowser's laugh is still heard on entry on the final lap, or when the player gets too close to the Bowser statue at the start of the track. It is the longest retro course in the game (as well as the longest course overall), taking around one minute per lap. The bridge that comes before the long circular turn before the end is now broken, with Lava Geysers on the sides. Additionally, the ramp after the spiral has a Dash Panel on it, making the jump easier. The Bowser portraits, which in the original used his artwork from Super Mario Bros. 3, now resemble his artwork from Super Mario Galaxy. Bowser's laugh that plays in the Wii version uses Kenny James's voice, which is the current portrayal of Bowser.

Tournaments
2009-TournamentMarch2.jpg In Mario Kart Wii, a tournament occurred on this course, which had players race against Dry Bowser, who utilized the ability to attack with fireballs. This tournament took place as the second tournament for March 2009, and it was restricted to karts. It was later repeated as the second tournament of June 2010, but without any restrictions. It was repeated for the third time as March 2011's second tournament, and the karts only restriction returned.

Mario Kart 64

 * Instruction manual: "Surprisingly, the Bowser's Castle has been transformed into a race ground! Because it's inside the building, most of the corners are tricky right angles. However, the most difficult part of the course is where the Thwomps are. They will block your path, and if you run into one, you will spin out. Should you be stepped by one, you'll find yourself squished flat as a pancake."
 * Website bio: "Bowser's Castle can be one of the toughest courses in the game if you don't know the way through it."

Mario Kart Wii

 * European website: "Racing over the red carpets in Bowser's not-so-humble abode might make you think you're in for a warm welcome from the king of the Koopas. Well, if fire-breathing statues are your idea of a warm welcome..."
 * Trading Card bio: "It's especially important to have great cornering skills for a track like N64 Bowser's Castle. Most of the corners are tight and if you cut them too close you'll run into a wall. Avoid the fire-breathing Bowser Statue in one of the courtyards by boosting through the grassy area. It's a nice shortcut."

Trivia

 * In the Mario Kart 64 instruction manual, there are triangles at the third bridge and between the jumps afterward telling the player(s) to watch for falling rocks, despite the fact that there are no falling rocks or any other obstacle in that area. This is actually a translation error; in the Japanese manual, this is merely a warning not to fall off the track, with the kanji used being similar to the ones used to describe the falling rocks in Choco Mountain.
 * A rumor popularized by videos in 2007 suggests that the Thwomp locked behind a cage at the beginning of the course, nicknamed "Marty", can be unlocked as a playable character by going around the statue of Bowser 3 times, doing the entire track in reverse followed by repeating the 3 circles around the Bowser statue again. However, no evidence in the data of the game suggests this, and one video showing the method as shown above was made to be an April Fools Joke.