Affiliate Marketing Secrets

basically i want to be tumblr famous, and i feel like a good way to do that is to have a funny, specific niche. (like blogs ike ‘white girl problems” or “ways to annoy people” or “dirty bieber secrets”) you know, blogs that only post about specific topics and specific themes…
so i was wondering, any good theme ideas? just something simple that a lot of posts could be made about and could be funny?
the more ideas, the better!