What was the most fun language to learn?

I don't know why people say that Haskell has such a steep learning curve. It's my second functional language (after a quick flirt with Scheme) and it's a blast to learn. Most fun I had since first learning Pascal. Other than Haskell, learning Perl was not that bad and obviously good old Pascal because it was easy to grasp in a matter of minutes.

So what about you, prog?

P.S. I'm curious to see the correlation between fun-to-learn and popularity, especially since, learning a new language is usually one of the most boring tasks for a programmer.

Probably Common Lisp. I'm still terrible at it, but I really enjoy using it. Overall I still prefer Haskell, but I would say that CL is more "fun".