1. It could be scaled up a bit,
2. it could bounce twice near the kart before going quickly towards the first karts,
3. a more cartoonish "booing" sound would be nice when it bounces, I did not find exactely the one I have in mind, neither could I reproduce it on Audacity, but maybe like this one (but there is too much reverb. here) or this one (I prefer the first but this one doesn't have reverb). I am looking for the kind of sound we can expect the 1st ball in this little video to produce... not simple to explain with words ^^!
These improvements would enable the player to understand more easily what's this ball, and would be funnier I think.
PS : And if you want an icon, I can try to make one
