The "Boo Classic" tournament is misspelled in-game as "Boo Clasic".
Wario's shoes are erroneously colored pink in this game when they should be green like in the promotional artworks and other games he appears in.
When Princess Peach scores an Eagle or better, she does her animation pose where her mini-dress takes the form of a full-length dress like she normally wears outside these sports titles, but it lacks the secondary color of being magenta from when it went up to above her knees. In the later game "Mario Tennis", her mini-dress was given the magenta pattern at the ends of the skirt to be consistent in appearance with her normal dress.
One of two Mini-Golf courses Peach's Castle - despite the name, her castle does not appear and instead its background scenery shows ice cream, lollipops, and other sweets.