They are two have different things. If someone is potty or going potty, that means they are crazy or going crazy.
Here are these examples:
My boss wants me to work in New Year's Day for no extra money. He must be potty.
She's potty to sell off her old cars so cheaply.
There is another meaning to " potty". If someone really keen on something we can phrase " to be potty about something".
I really like Japanese comic books, I'm potty about them.
I'm potty about miniature owls: I've got nearly one hundred of them at home.