This Weekend Genius Challenge is short but sweet. The five words in the list below have something specific in common. While there are multiple answers to this particular query (for instance, they all contain the letter "i") only one answer will match ours. If you're the lucky first to do so, you'll win a T-shirt of your choice from the mental floss store. The words:

bicentennial, hallucinogen, hitchhiker, reincarnation, unfamiliar.

Answer by commenting below. Please include what style/size of T-shirt you'd like in your response. The correct answer will be revealed Monday, unless we don't yet have a winner, in which case we'll add a few words to the list and continue the challenge. Good luck!