I Know For A Fact - A phrase used when you want to sound smart but are actually

A phrase used when you want to sound smart but are actually just full of hot air and nonsense.

I know for a fact that your video game character is better than mine. Also, I know for a fact that you’re wrong.

I know for a fact that your mom is a witch. She probably makes potions out of your lunch.

I know for a fact that you’re lying. I also know for a fact that I’m right.