Slots are the places that Nintendo tracks or Custom Tracks run on. Mario Kart Wii has 32 track slots organized into 8 cups with 4 tracks each. The slots are numbered from 1.1 (first cup, first track) up to 8.4 (eighth cup, fourth track). Nearly all slots have special features.

Race Courses
Cup	Slot	Track	Music ID	Special Slot ID
Mushroom Cup	1.1	Luigi Circuit	0x75	0x08
	1.2	Moo Moo Meadows	0x77	0x01
	1.3	Mushroom Gorge	0x79	0x02
	1.4	Toad's Factory	0x7B	0x04
Flower Cup	2.1	Mario Circuit	0x7D	0x00
	2.2	Coconut Mall	0x7F	0x05
	2.3	DK Summit	0x81	0x06
	2.4	Wario's Gold Mine	0x83	0x07
Star Cup	3.1	Daisy Circuit	0x87	0x09
	3.2	Koopa Cape	0x85	0x0F
	3.3	Maple Treeway	0x8F	0x0B
	3.4	Grumble Volcano	0x8B	0x03
Special Cup	4.1	Dry Dry Ruins	0x89	0x0E
	4.2	Moonview Highway	0x8D	0x0A
	4.3	Bowser's Castle	0x91	0x0C
	4.4	Rainbow Road	0x93	0x0D
Shell Cup	5.1	GCN Peach Beach	0xA5	0x10
	5.2	DS Yoshi Falls	0xAD	0x14
	5.3	SNES Ghost Valley 2	0x97	0x19
	5.4	N64 Mario Raceway	0x9F	0x1A
Banana Cup	6.1	N64 Sherbet Land	0x9D	0x1B
	6.2	GBA Shy Guy Beach	0x95	0x1F
	6.3	DS Delfino Square	0xAF	0x17
	6.4	GCN Waluigi Stadium	0xA9	0x12
Leaf Cup	7.1	DS Desert Hills	0xB1	0x15
	7.2	GBA Bowser Castle 3	0x9B	0x1E
	7.3	N64 DK's Jungle Parkway	0xA1	0x1D
	7.4	GCN Mario Circuit	0xA7	0x11
Lightning Cup	8.1	SNES Mario Circuit 3	0x99	0x18
	8.2	DS Peach Gardens	0xB3	0x16
	8.3	GCN DK Mountain	0xAB	0x13
	8.4	N64 Bowser's Castle	0xA3	0x1C

The arena slots are arranged into 2 cups with 5 arenas each.

Battle Stages
Stages	Slot	Arena	Music ID	Special Slot ID
Wii Stages	1.1	Block Plaza	0xB7	0x21
	1.2	Delfino Pier	0xB5	0x20
	1.3	Funky Stadium	0xB9	0x23
	1.4	Chain Chomp Wheel	0xBB	0x22
	1.5	Thwomp Desert	0xBD	0x24
Retro Stages	2.1	SNES Battle Course 4	0xC3	0x27
	2.2	GBA Battle Course 3	0xC5	0x28
	2.3	N64 Skyscraper	0xC7	0x29
	2.4	GCN Cookie Land	0xBF	0x25
	2.5	DS Twilight House	0xC1	0x26

There are 5 other slots reserved for Galaxy Colosseum and the winning/losing scenes.

Other
Track	Music ID	Special Slot ID
Galaxy Colosseum	0xC9	0x36
winningrun_demo	—	0x37
loser_demo	—	0x38
draw_demo	—	0x39
ending_demo	0x75	0x3A

Special Slots

Most tracks run on all slots, with exceptions of slots 4.2, 6.1 and 6.2; additionally, some tracks only run at slots 3.1, 5.3 and 7.1. Here are the rules for these special slots:

Tracks can only run on slot 4.2 if they have at least one instance of kart_truck and car_body and have the special MDL0 from the original track containing polygon11 and polygon60.
Tracks can only run on slot 6.1 if ice.brres is present; furthermore this object is necessary to activate the icy water fall boundary flag, which only works at this slot.
Tracks can only run on slot 6.2 if HeyhoShipGBA is used; also objects HeyhoShipGBA and HeyhoBallGBA only work on this slot.
Tracks using objects sunDS, FireSnake and pylon01 only work on slots 3.1 and 7.1.
The object poihana sometimes doesn't work on slot 5.1; curiously, the object is used on this slot by Nintendo.
Tracks using objects obakeblockSFC, obakeblock2SFC and obakeblock3SFC only work on slot 5.3 if these objects are intended with fall animation, but here they are not scalable; on all other slots these objects can be scaled but they are unsolid and without animation. Wiimms SZS Tools use them to make item and enemy routes visible during gameplay or to mark positions.
All other slots are different for KCL Sound Triggers, particular sounds or GFX for KCL flags or what effects they give to tracks.

Slot Expansion

It is possible to expand the track selection list to include more slots. It should be noted that new slots have no unique slot features, but can use special slot effects and music slots.

Unique and Special Slot Features

Slot 1.1 (Luigi Circuit)

Unique

An audience ambience plays in the background indefinitely if the KCL Sound Trigger is not used.

Music

Slot 2.1 uses the same background music files.

Slot 1.2 (Moo Moo Meadows)

Unique

During the opening cameras, sounds of cows and bells can be heard.

Slot 1.3 (Mushroom Gorge)

Unique

Wind ambience plays in the background indefinitely if the KCL Sound Trigger is not used.

Special

There is always a white fog in the middle of the screen and other random clouds of fog throughout the course. However, the fog on the screen can be replaced with an AREA that uses spores.
Sand off-road is dark gray.
Jump Pad with variant 4 has SFX, but the SFX works in the kinoko_bend object KCL, regardless of slots.

Slot 1.4 (Toad's Factory)

Unique

An audience ambience plays in the background indefinitely if the KCL Sound Trigger is not used.
KCL Sound Trigger can be used to trigger alternate channels in a multi-channel BRSTM among other sound effects. This can also cause problems with BRSTMs that do not have multiple channels.

Slot 2.1 (Mario Circuit)

Special

Sand off-road is a lighter color.

Music

Slot 1.1 uses the same background music files.

Slot 2.3 (DK Summit)

Unique

An audience ambience plays in the background indefinitely if the KCL Sound Trigger is not used.

Special

It is always snowing, which can only be disabled with AREA type 1.
The cannon sound and little wooden gate sounds can be heard when encountered.
Posteffect fog clears up at around 45 seconds.

Slot 2.4 (Wario's Gold Mine)

Unique

KCL Sound Trigger can be used to trigger alternate channels in a multi-channel BRSTM among other sound effects. This can also cause problems with BRSTMs that do not have multiple channels.

Slot 3.1 (Daisy Circuit)

Special

The object cruiserR only works properly on this slot; it might work in other slots, but not the way it is supposed to.
There are some tracks that do not work on this slot (such as tracks based on Dry Dry Ruins). It is unknown why.
Objects sunDS, FireSnake and pylon01 only work on this slot and 7.1.
The object sound_audience only works properly on this slot.

Slot 3.2 (Koopa Cape)

Unique

KCL Sound Trigger can be used to trigger alternate channels in a multi-channel BRSTM among other sound effects. This can also cause problems with BRSTMs that do not have multiple channels.

Slot 3.3 (Maple Treeway)

Special

Sounds of the cannon can be heard.
Grass off-road is olive-colored.

Slot 3.4 (Grumble Volcano)

Special

Objects VolcanoBall1 and VolcanoPiece have SFX.

Slot 4.1 (Dry Dry Ruins)

Unique

KCL Sound Trigger can be used to trigger alternate channels in a multi-channel BRSTM among other sound effects. This can also cause problems with BRSTMs that do not have multiple channels.

Special

Sand off-road is a darker color.

Slot 4.2 (Moonview Highway)

Unique

KCL Sound Trigger can be used to trigger alternate channels in a multi-channel BRSTM among other sound effects. This can also cause problems with BRSTMs that do not have multiple channels.

Special

Tracks work only if there is at least one instance of every car type (so, a normal car, a truck, and a bomb car) and the course_model.brres must be the original with polygon11 and polygon60.
Getting hit by anything grants the driver invincibility to cars and trucks for a short duration of time.
The wheels of traffic hazards only animate on this slot.

Slot 4.3 (Bowser's Castle)

Unique

KCL Sound Trigger can be used to trigger alternate channels in a multi-channel BRSTM among other sound effects. This can also cause problems with BRSTMs that do not have multiple channels.

Special

Sounds of the cannon can be heard, although the character doesn't speak.
Grass off-road is brown.
Sand off-road is black.

Slot 4.4 (Rainbow Road)

Unique

KCL Sound Trigger for gate sounds is present.

Special

Sounds of the cannon can be heard.
The camera has a different angle while taking a cannon.
KCL flags 0x00F7 and 0x00B6 have a special sound when drifting.
KCL flag 0x009E has a special sound on collision.
Hitting the backside of something drivable with a Bullet Bill results in a fall boundary.

Slot 5.1 (GCN Peach Beach)

Special

Grass off-road is light-green.

Slot 5.2 (DS Yoshi Falls)

Unique

A bird ambience plays in the background indefinitely.

Slot 5.3 (SNES Ghost Valley 2)

Special

The original track has 645 global objects, 602 of which are obake blocks. The average number of objects in all other tracks is 73; this is the only slot that supports that many objects. Using the track in other slots would cause objects to malfunction, e.g. invisible item boxes.
Objects obakeblockSFC, obakeblock2SFC and obakeblock3SFC are solid and animated only on this slot, but they aren't scalable; on other slots they are scalable but they are unsolid and not animated.

Slot 5.4 (N64 Mario Raceway)

Unique

An audience ambience plays in the background indefinitely if the KCL Sound Trigger is not used.

Special

Sand off-road has a lighter color (lighter than Mario Circuit).

Slot 6.1 (N64 Sherbet Land)

Unique

KCL Sound Trigger can be used to play an icy cave ambience.
Objects penguin_s and penguin_m have SFX.

Special

Only courses including ice.brres run at this slot.

Slot 6.2 (GBA Shy Guy Beach)

Unique

A marine ambience with seagulls plays in the background indefinitely.

Special

Only courses including the object HeyhoShipGBA can run at this slot and those tracks don't work on other slots.

Slot 6.3 (DS Delfino Square)

Unique

A Pianta audience ambience plays in the background indefinitely if the KCL Sound Trigger is not used.

Special

Grass off-road is yellowish-green.

Slot 6.4 (GCN Waluigi Stadium)

Unique

An audience ambience plays in the background right away, but only for a few seconds.

Special

Applauses for each trick can be heard.
The GFX color of Mud off-road is grey.

Slot 7.1 (DS Desert Hills)

Special

Objects sunDS, FireSnake and pylon01 only work on this slot and 3.1.

Slot 7.2 (GBA Bowser Castle 3)

Special

A thunderstorm ambience plays in the background right away, but only for a few seconds.
Sand off-road is red.

Slot 7.3 (N64 DK's Jungle Parkway)

Unique

A jungle ambience plays in the background indefinitely if the KCL Sound Trigger is not used.

Special

KCL flag 0x0020 has dirt GFX.

Slot 7.4 (GCN Mario Circuit)

Unique

During the opening cameras, sounds of a Chain Chomp can be heard.

Slot 8.1 (SNES Mario Circuit 3)

Special

Sand off-road is a lighter color (darker than Mario Circuit).

Slot 8.2 (DS Peach Gardens)

Unique

During the opening cameras, sounds of Chain Chomps can be heard.
A bird ambience plays in the background indefinitely.

Special

KCL flag 0x0021 is a lighter color.

Slot 8.3 (GCN DK Mountain)

Unique

A jungle ambience plays in the background indefinitely if the KCL Sound Trigger is not used.

Special

KCL flag 0x0020 has dirt GFX.
The object DKrockGC has SFX.

Slot 8.4 (N64 Bowser's Castle)

Unique

Random coughs of the Bowser roar and fireball can be heard.
KCL Sound Trigger for the Bowser roar is present.