Use a "turbo" (or similar) controller and keep the Circle and Square buttons held to raise your power meter very easily. However, be warned that the game will recognise this as cheating and display "USING CHEAT" above your meter.
Get a distance where the numbers before and after the decimal are the same (eg. 24.24, 38.38...) to see balloons released from the crowd.
Get a distance where all three numbers are identical (eg. 2.22, 3.33...) to see a mole behind the crowd.
Get a distance where all three numbers are identical (eg. 2.22, 3.33...) to see a dinosaur behind the crowd.
At the select game screen, hover over "100m Free Style" and press Up, Up, Down, Down, Left, Right, Left, Right, Circle and X. All players will now be in bikinis.