Ultra

Ultra shortcuts, also referred to as ultras or KCP skips, are a major glitch in Mario Kart Wii that allows players to complete laps without hitting all of the necessary checkpoints. Ultra shortcuts allow for the largest combined timesave out of all glitches in the game; as such, they are banned in the No Ultra and No Glitch categories.

Overview

Ultra shortcuts are possible because of an oversight in the checkpoint system. Each track features a few special checkpoints, called key checkpoints or KCPs, and the finish line checkpoint, or KCP 0, which control what checkpoint regions are active. The intended method for counting a lap is driving in all KCPs in order, to activate each checkpoint region one at a time until reaching the finish line; if a KCP is skipped, the checkpoint regions stop updating, and the finish line checkpoint is not active, making it impossible to get a lap count.

However, it is not necessary to drive into all KCPs in order to get a lap count. The only necessary conditions for getting a lap count are: KCP 0 must be active, and the vehicle must drive into the last KCP before KCP 0. Completing a lap without hitting all the checkpoints in order is known as an ultra.

Last CP rule, 95% rule

The game features two failsafes to attempt to prevent ultras:

• Driving from KCP 0 to the last (regular) CP always decreases the lap count by 1 (last CP rule);
• If the Lap% value (which tracks lap progression) increases by over 0.95 at once, the lap count is decreased by 1 (95% rule).

As such, performing an ultra involves driving from KCP 0 to any checkpoint in the final KCP region, except the last CP, while increasing the Lap% value by less than 0.95 upon entering the new checkpoint, to avoid losing a lap. Since the last KCP is active while being in KCP 0, it is possible to simply drive to the last KCP and back to KCP 0 and get a lap count.

Reverse ultra

Although it is generally not useful, it is also possible to perform ultras in reverse to decrease the lap counter without driving through all KCPs.

The mechanics and failsafes involved in reverse ultras are very similar to the regular case, but applied in reverse. Reverse ultras are performed by driving from any checkpoint in the last KCP region, except the last one, to KCP 0, while decreasing the Lap% value by less than 0.95.

Known ultras

Main article: List of ultras

Currently, ultras have been discovered on 29 of 32 tracks in the game. 3 of the 29 ultras are usually referred to as ultra longcuts, as performing them is slower than simply driving through all KCPs; the other 26 are known as ultra shortcuts, and save time on at least one category.

The following table lists the viability of ultras on each track.
  Ultra shortcut, implemented in the TAS
  Ultra shortcut, not yet implemented in TAS
  Ultra longcut
  No known ultra

History

Discovery

The first track to have an ultra was Grumble Volcano. Discovered by Ridley on June 1, 2008, it involved driving one lap of the race around a raised rock to the left of the finish line, which had drivable collision.

"I have discover a new SC in Grumble Volcano
I can make a lap in 10 seconds
It's not a fake I make a time and you can take my ghost"
—Ridley, Mario Kart Message Boards.

Only hours later, it was proven possible on all 3 laps. On June 1 alone, 18 runs lowered the world record from 1:46.052 to 23.512. Later that month, player Green Bean (Japanese: インゲン) found the game's 2nd ultra shortcut, and unveiled a 55.141 on Mushroom Gorge.

Figuring out how these ultras worked would be crucial in determining viability on other courses. A, well-known modder, MrBean35000vr, figured out the basics of the game's checkpoint system around August 2008, and used this new knowledge to demonstrate an ultra on Wario's Gold Mine using speed hacks.