Well, Fun Stuff is a board, while What Made You Laugh is a thread. You're not really breaking any hard rules by posting this as a separate thread, but we do have several long-running, well frequented, generic threads in the Fun Stuff board, so that the board doesn't get drowned (when the traffic picks up, ehm) in a ton of threads that are unlikely to have more than just a couple of replies.
There's What Made You Laugh/Sad/Astonished, Yarn of Insignifcant Questions, What's On Your Mind and Random Media or The More You Know.
What Made You Laugh is typically personal stuff that happened to you recently. Maybe fun with friends/family or topical news/events.
Fun Stuff is more general, and can be anything found in various corners of the Internet.