CatRaccoonBL
You can do it!
Thats a pretty good looking side smash all things considered. It has quite the range like Mii Gunner, but at the same time it will probably have a lot of power behind it judging by it's slow speed.The air attack where the Clown Car spits out a cannonball for Jr to pick up and then immediately drop, and a special that deploys a mechakoopa (we're guessing down special)
Oh and the cannon ball shot might actually be a side smash due to the yellowish flash that appears a split second before he fires. This is just a pure hypothesis right now though.
EDIT: Thank you RascalTheCharizard for uploading almost every notable thing Jr does in gif form on page 27
See the flash?