Fast fun plant for my grow box between grows

I enjoy growing so much that I would like to grow something fast and fun between my "other" grows. I don't smoke much so I don't plan on growing again for several months after my current grow is done. Can't see letting my grow box go unused since I love it and invested so much time and money. Preferably a vegetable that takes a 8-12 weeks to mature. Any ideas appreciated. The more exotic the better. I can be swayed to fruit or flowers if they sound fun/cool enough.

tomatoes, usually 70ish days till fruit
peppers, little longer
any lettuce will be fine
water mellon is 80/85ish days to harvest
hit up walmart seeds are cheep, and the back of the packs say how long they take. you could get a nice little indoor garden going pretty easy, window boxes will hold 3-4 heads of lettuce, 3-5 gallon buckets for tomatoes, 3-4 vines per window box(water mellon, pumpkin, cucumber)

and most flowers will be fine in that time period too

best of luck

i think chinese lanterns look neat i am trying to grow some right now

herb..like basil, dill, rosemary, sage....

yea Id say herbs are more worthwhile. Spending three months for a watermelon..