How do i make, for example, a player (someone else's player) shape to be a ball?
I'm not allowed to provide you with a script but I'm able to give you hints.
CurrentCamera
This will allow you to modify the camera
http://http://wiki.roblox.com/index.php?title=API:Class/Workspace/CurrentCamera
CameraSubject
This will let you define the camera
http://http://wiki.roblox.com/index.php?title=API:Class/Camera/CameraSubject
KeyDown
This will allow you to detect key inputs
http://http://wiki.roblox.com/index.php/Taking_keyboard_input