Hit the hay

To 'hit the hay' means to go to bed.  It recalls a simpler time when people may have slept in a barn.

Example:

-Okay, kids!  Time to hit the hay!

-Aw!  5 more minutes?

Head-butt and butt heads

If you are 'head-butted,' it means someone has bumped or hit you with their head. It's usually something kids or pets do. Interestingly, it different from but related to 'butting heads.' This is when two people keep disagreeing and can't reach any consensus, as if their heads were actually bumping, or butting, together.

Examples:
-Your cat keeps head-butting me. I think she likes me.
-She just wants to get her smell on you.

-Dad and I just don't agree on anything! It's so frustrating to talk to him.
-Yeah, you guys do butt heads a lot!