Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo

James, while John had had "had," had had "had had"; "had had" had had a better effect on the teacher.

https://en.wikipedia.org/wiki/James_while_John_had_had_had_h...

I always felt explanations for this were even more confusing. Best to replace the adjective, noun, and verb with completely different words:

Toronto cats Toronto cats harass harass Toronto cats.

Reminds me of: https://en.m.wikipedia.org/wiki/Lion-Eating_Poet_in_the_Ston...

The best bit:

any sentence consisting solely of the word "buffalo" repeated any number of times is grammatically correct

My favorite sentence.