I absolutely LOVED "Speed Racer"...I keep waiting for more people to discover it, but sadly it's been four years and I'm afraid no one else will :cry
As for the keys, that M&M figurine tip sounds like a good start for the keychain. As for the key, do you have a screencap of its tip? For the key, I'd go with wood/wood dowel with a small rectangle of styrene for the tooth. Maybe red plastidip for the key cover? Finish it off with white waterslide decals for the "M" logo.
Good luck, Nick!