Talk:Epic Rap Battles of History 52/@comment-24408988-20141216004518/@comment-98.222.132.11-20141216014218

From wikipedia -

"Use of a sexually-derived expletive will automatically incur a PG-13 rating, while multiple occurences will usually incur an R rating. Usage of such an expletive in a sexual context will also generally garner an R rating"

So basically anytime a sex joke is made and there's a swear word involved, it's an R-rating automatically.