My daughter isn't much into YouTube now but went through a phase of watching about an hour a day and, boy, she watched some bizarre stuff! I think she watched more obscure Russian and Slavic cartoons from the 70s than anything in English. None offensive, but certainly weird. I'm kinda hoping it rubs off in terms of being generally progressive and a weird arty person though.. we shall see ;-)

(And before anyone asks, being exposed to hours of non-English language content appears to have had zero effect in either a negative or positive way, alas.)