Bouncy Ball stuck in toilet
Go buy a new wax seal (well, ideally step aside as the plumber hired by the responsible parent comes and sorts this out, but I guess that's asking for too much.)

Swab out all the water you can, unbolt and remove the toilet; plug the open pipe with something you won't forget to remove before you replace the toilet - typically a rag and a plastic bag, to contain the sewer gas. 

Most toilet outlets are sufficiently restrictive that the ball is probably stuck in the toilet, presuming you mean the size of ball that would not represent a choking hazard to a small child. A small ball would flow through a toilet and the rest of the plumbing without causing problems until it got to the sewer treatment plant, in most cases. While you could try to hook it with a drain auger, removal is more likely with the toilet dismounted so that gravity isn't working against you and you can work from both ends, and if for some reason the ball got out (and then stuck), it might be lurking just below.

Or, if it's throughly jammed and you can't get it loose, you buy a new toilet (...or the responsible parent does...)