They: "Lol those movies are so inaccurate, the truck is playing music, but a few minutes later still has ice cream..."
Friend: "That's... That's how they work???"
If you wear armor that you lack proficiency with, you have disadvantage on any ability check, saving throw, or attack roll that involves Strength or Dexterity, and you can’t cast spells.
This is the internet, you prolly don't really want to know.