4chan is a website, I wouldn't go there, just in case. It is, as an entity, the most powerful thing on the internet. There's some pretty messed up stuff there, though, which is why it's funny that they've taken such an interest in a My Little Pony show.
It's an image board, it's vaguely similar to Deviantart, but it's format might confuse you at first. Not all parts are bad, you just want to stay away from /b/ (one of the sub-boards) and similar sub boards. /co/ is safe; in fact, they're some of the first ones to get their hands on "Friendship is Magic" and /b/ helped to really ignite interest on the internet.