Hey cam somebody tell me how to get the last star of the last castle in..

Ya, that is a tricky one to get. Here is how to get that star:
When you reach the checkpoint, go further on past the huge crunching flower and you should come to a ? Box. Above that, there is a small hole. That is how you get to the last star in that level. But, you'll have to go a bit further on and drop onto the first skeleton guy you come across after the hole in the roof of the ice. This will give you plenty of space to run back and jump onto the box!!!(It takes timing, precision and patience to get onto that box!) Once you make it onto the box, jump up to the roof hole and try and kick off the left side of the hole, like you would with a wall, and walljump onto the top of the screen(this also takes timing, precision and patience!) Run along that path and be careful of the tiny hole right of the running tape. Just hold X or Y to dash across the tiny holes to get the Last Star in the Last Castle on World 5.
I hope you have found this information useful!!!