A boy's boys' boys night out

A night out; for one boy; with his boys; typical of boys.

*puts on linguistic analysis hat*

It is that boy's night out. 

(singular possessive)

That boy is having a night out.

It is the boys' night out. 

(plural possessive)

Tonight belongs to the boys.

It is a boys night out. 

(noun as adjective, compound noun, collocate)

A night out typical of boys.

I think I'm *more* confused now...