Super Tennis is a surprisingly decent Tennis game. But I can tell, sometimes you want to mess with it. Change it around somehow.
And you can!
First, start a match
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Then hit Select on Controller 1 to pause the action
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Grab Controller 2 and hit
R, R, Left, Down, B, A, L, L
Then grab Controller 1 and hit B. Done right, you'll see a screen full of gobbledygook come up.
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Which is actually a whole bunch of statistics, which you can change to whatever you want. And since they're in Base 16, the highest thing you can adjust them to is 'F'.
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And there are four pages of them to change, so you might be there for a second or two.
Then you go back to the game an notice... well... not much, really. But at least I know that my Tennis Star's stats are maxed out, even though they don't seem to do much.