This is a sweet little story. I think hat you capture Rikku's voice well and I like the thought of Rikku feeling maybe a little left out of Tidus' homecoming and seeking to gain some of her friend's attention by jury-rigging some fireworks.
I like Rikku's arrogance and the way she actually does know she's not the best at mixing - the paperclips and spit amuse me greatly.
I like the way that Tidus takes great delight in his knowledge of Al Bhed, except I think he should know that Yuna has learned it too. Hee.
I really love the way that Rikku is so excited that everyone is enjoying the spectacle because of her. She seems very proud of herself, more so maybe than because of saving the world, even though she demands her share of glory from that too.
I really like the attitude you have given Rikku and I really enjoyed this little story.
I like how Tidus suspects Rikku of attempting to blw up the Temple. Hee.