Mechanic that makes character larger in size

Good day!

I want to add a mechanic that makes the player grow in size and/or shrink (and maybe even change the body shape) when a certain condition is met, for example, you grow tall and muscular when you drink a certain potion, or you shrink and get thin and flimsy when it is daytime, etc.

I have no idea how to do this. To be honest I am a begginer, and I couldn't find anything in the wiki that could help. 

How can I do something like this with MCreator?

Thanks for your attention! Sorry for my bad english. Have a good day