What is It's Casual?
1.
1. It's all good.
2. Don't Worry
From 1984's The Wild Life
Tom: Will you marry me?
Eileen: What?! No!
Tom: It's casual.
See
2.
it's ok, don't fret or worry
from 1990's Mega Morphin Power Rangers:
"Sorry about that"
"Forget it, it's casual"
See