Mario Power Tennis/Unlock Characters and Courts

At the start, you have almost all characters, but limited courts. Here's how you unlock the rest.

Characters
The way you unlock them is pretty straightforward. There are no tricks, but it's not too hard, with the exception of the very last part of the sixth tournament.
 * Koopa Paratroopa can be unlocked in the first three doubles tournaments.
 * Fly Guy can be unlocked in the first three singles tournaments.
 * Petey Piranha can be unlocked through the Fire and Thunder Doubles Cups.
 * Wiggler can be unlocked through the Fire and Thunder Singles Cups.

Courts
Besides the normal and gimmick courts there's still a few more to unlock.
 * You can unlock all options on a special court, just play on that court in Special Cup.
 * Bowser Castle Court can be unlocked through Fire Cup of Gimmick Masters in singles and doubles.
 * Mario Classic Court can be unlocked through Thunder Cup of Gimmick Masters in singles and doubles.