No, it can't. In this sentence, 'fun' is being used as an adjective. Strictly speaking, 'fun' is a noun, but it is often used as an adjective in informal language. Here are some examples: He's a fun guy. That sound like a fun game. It was fun to hang out together.

In American dictionaries, fun is listed as a noun, a verb, and also as an adjective, but as Su.ki said, this is an informal usage and it is marked as such. See the adjective definitions at: 1. http://www.learnersdictionary.com/definition/fun and 2. 1. http://www.merriam-webster.com/dictionary/fun From a formal writing point of view, I would say that you shouldn't mix fun with easy since the two words on either side of "and" aren't from the same grammatical group. However, if you are writing something like a novel in which one of the characters is speaking informally, then in my opinion at least, it would be okay to mix them since this actually happens in real world informal settings and it develops the character. You can't have a character who is from some small hick town speaking with perfect English after all. :)