Yes.
by getting all gold in a cc
Rob the Robot
No, Boo isn't in Mario Kart Wii.However, King Boo is unlockable in the game by winning a gold trophy in the 50cc Star Cup.
By winning gold in all the cups, so the 50cc, 100cc, 150cc and 150ccMirror(unlock this one by getting at least one star in the other cups)
keep getting first on hard tracks
First, you have to unlock the Mirror Mode of the Mario Kart game by winning all the 150cc cups with gold. Then, you have to unlock the Lightning Cup. By unlocking and winning the Mirror Lightning Cup in Gold, you can unlock the Blue Falcon. It's good you asked, because the Blue Falcon is an amazing kart. It is very fast. (Just try not to go offroad with it)
By winning races moron...
You unlock Daisy by winning the 150cc Special Cup!
By winning other Grand Prixes.
Unlock additional "cups" by winning a cup trophy.
I unlocked him by winning first place in the 100cc leaf cup.
There are no way of getting a baby waluigi on Mario Kart there are only two baby's on Mario kart: Baby Mario and baby Peach unless there is a cheat to it that I am unaware of