This sentence is false.

Visiting relatives can be annoying.

Colorless green ideas sleep furiously.

ah kee ess oon ah may sah

Spanish speakers and Yiddish speakers will interpret the string differently, but it will be taken as grammatical in both cases.

Buffalo buffalo buffalo buffalo buffalo buffalo buffalo buffalo buffalo buffalo buffalo.

(That last sentence is grammatical. Compare to: Canadian geese Siberian tigers intimidate deceive European swallows Indian elephants intimidate.

The next two are also grammatical.)

The boy the girl the cat bit scratched died.

The girl the cat the dog the farmer owned chased scratched fled.