I'd say my favorite moments have to do with Mario. Whenever he misses a ball, I crack up when I hear him say ''Ouch!'' two times. Also, that motion he makes when he loses a match seems to emphasize for me that I've won a match against him.
And of course, who could forget that motion Luigi makes when he loses a match? Luigi is SUCH a sore loser.
And there was that one match versus Baby Mario where I was having a hard time keeping up. Anyway, he was setting up for another power shot, and I thought I'd lose the point again. But instead the ball jumped over his head, so I got the point instead.
I also crack up when someone double faults.
Finally, I just burst out laughing that one time where I was in a doubles match with Bowser and Boo as opponents. Bowser serves the ball, but it whacks Boo in the back of his head instead. You'd think that a ball flying at 100+mph into your head would hurt.
Peaceful penguins, demented dragons and growling griffins, oh my.