Or everything else in the game that doesn't belong on any other page
Ghost: If all your balloons are popped in a battle with two or more human players, you will be permanently a ghost until the game ends (everyone but one person is out).
Item box: You can lay a real item box as a ghost!
Red shell: It never follow you on some shortcuts and take the intended route, then waits.
Blue shell: Can track you over any shortcut, intentional or otherwise.
Computer players: Never attack each other if you are far enough behind or in front of them.
There is a lighthouse in Cheep Cheep Beach.
Desert Hills has many Mario Bros 3 references including red pipes and pyramids. And the angry sun enemy.
Delfino Square has various shop names to look out for as you use the alleys.
Waluigi pinball has a slot machine with the pictures of items on it.
Shroom Ridge has a van which says fish on the side with the picture of a cheep cheep.
There is an unreachable frozen lake in DK pass.
Mario Circuit has the castle from Super Mario 64 as part of the background.
There are Super Mario Bros pipes in many levels.
Airship fortress has a castle in the background.
The banners on Wario Stadium are Mario themed.
Peach Gardens has much outside of the track. You can throw an item out of the level too.
Luigi's Mansion is in the background of the Gamecube version of Luigi Circuit.
There is a sign in Moo Moo Farm saying the name.
Frappe Snowland has Mario and Yoshi ice statues.
Baby Park has a ride called Kamek's Magic Show.
There is a danger sign on Choco Mountain.
Mushroom Bridge still has some Gamecube features as background details.
Choco Island 2 has the background from the Chocolate Island Levels in Super Mario World.
The fish from Banshee Boardwalk is in Super Mario 64 DS.
Sky Garden has the Luigi Blimp.
You can ride on the barrier in Bowser Castle 2.