My stepdad is a great and nice guy, and I've suspected for a while that he might be autistic. He's very quiet and reserved, rarely shows strong emotion. Chuckles rather than laughter. He's also fixated on certain things and hobbies, and can talk/ramble about them for quite a long time. He likes puzzles and, what have been given to him, legos. Putting together and taking apart things.
Like I said, no hard evidence, but I could see it.
In his case, I think he likes/understands sarcasm and makes sarcastic jokes pretty often.
It seems autists tend to either not get sarcasm or have it practically be their first language (I am in the latter camp).