Paddle Mania stretches the definition of Paddle Tennis as far as it can go before snapping into full blown chaos.
Unused Court Content
All courts are designed to be 256 pixels wide. Only 240 pixels worth of content are ever shown, leaving a 16 pixel width strip of the court unseen. In this case, it doesn't really matter much, since all that's missing is a bit of the service box.
The Sumo, Surfin, and Pool courts have unused tiles in the graphics ROM meant for earlier court layouts, though their tilemaps are no longer in the game. In this case, the early court has goals of equal width for both sides and a different service box design.
Most of the parasol and a few of the sunbather's tiles are never seen in the game proper.
The alternate court design is significantly easier for the player(s), with more decorative walls and a nice green welcome mat.
There's nothing really unused in the full Pool court, that image is just here for comparison with the alternate layout. Said layout has a number of features that the final layout does not, including lane markers, a properly marked service box, and a "GOAL" graphic at the end of the pool.
High score names are limited to six characters. However, three of the default high score names are seven letters long. As a result, "CRAPTON", "BAILLEY", and "GABRIEL" have a character cut off at the end. The full list of names can be found in the main CPU at 0x0266E.
Starting at 0x21B60 is text for an early Court Select.
COAT A COAT B COAT C COAT D COAT E
The D and E strings are actually further apart than the A through C strings, hinting that those courts were added later in development.
At 0x2285E is a more properly spelled, but improperly spaced, set of court text:
COURTA COURTB COURTC COURTD COURTE
Like the older text block, Court D and Court E aren't grouped with Courts A-C.