Most of this information is head canon that I assumed from actual canon. They hint at alot about Sasori, but they never really come right out and say these things. Gotta love it when they leave it to your imagination. lol
1. Despite his youthful teenage appearance, Sasori is actually in his mid- to late thirties.
2. Sasori had been missing from his village for twenty years before he was discovered to be a member of the criminal organization called Akatsuki during the kidnapping of Suna's Kazekage. The Kazekage is the leader of the Sand Ninja much like the Hokage is the leader of the Leaf Ninja.
3. Sasori is known amongst the ninjas as Akasuna no Sasori (Sasori of the Red Sand). His name, Sasori, translates literally into scorpion. A very fitting name for him if I do say so myself.
4. Sasori is the Puppet Master and almost all puppets used in the ninja world were originally designed by him. One of the hero characters named Kankuro uses puppets designed by Sasori.
5. Sasori is extremely impatient to a fault. He hates to wait and hates making other people wait. He becomes exceptionally ill-tempered otherwise.
6. A funny fact! Sasori has no man bits. You know why? It's because he turned himself into a puppet using his human puppet technique. He's nothing but an animated wooden body full of weapons and poisons.
7. I speculate one of the reasons Sasori did this was to make himself the ultimate puppet master ninja. He rids himself of pointless emotions, and takes away the factor that most puppeteers are long range fighters. Sasori can now fight from any range, though he still prefers long range.
8. Speaking of emotions, it appears Sasori didn't get rid of those as well as he'd hoped he did. Last I checked anger was definitely an emotion. You also see him looking shocked a couple of times, too. Maybe even a little remorseful at one point, but nothing was really said there. I play Sasori as having his emotions buried extremely deep inside of himself. It'd take a genius knowing the right buttons to push to bring those out, though. Except for anger and annoyance... those come out just fine by themselves.
9. When Sasori was a small child, his parents were killed by Konoha's White Fang. His grandmother Chiyo wanted revenge. Sasori holed himself up.
10. Sasori's grandmother Chiyo taught him everything she knew about puppets, so in a way she's to thank for the monster he became. She blamed herself for it at least.
11. Sasori missed his parents so much that the first puppets he ever made were created in their likeness. Of course, he soon realized that they couldn't be replaced. Sasori developed a strong distaste for death at this point.
12. Another reason Sasori turned himself into a puppet was possibly to cheat death. He says things off and on hinting to his desire for immortality.
13. Sasori didn't only turn himself into a puppet. He used that technique on nearly 300 other shinobi and added them to his 'beloved collection'. It's said he conquered a small country with his army of puppets. Definitely a force to be reckoned with.
14. Sasori is a master of not only puppets, but of poisons. The poison he uses the most is so intricate that he still has to use a reference recipe to make sure it is accurate. It slowly immobilizes its victims and usually kills them three days later after much pain and suffering. An antidote is said to be impossible to make. Haruno Sakura is the only medical ninja to ever successfully make an antidote for his poison.
15. There is a part of Sasori that is still human. There is a cylinder covered in roots that his name engraved on the surface. It's placed inside a cavity in his chest. It's the only bit of true flesh on him. To kill him, you have to pierce that cylinder, otherwise, you're wasting your time.
16. Sasori affectionately calls his puppets art that is eternal and last forever. He sees himself as an immortal artist of death.
17. Don't argue with Sasori about art. It's a touchy subject with him and if you don't agree with his views he will get hostile with you to the point of trying to kill you.
18. Despite not liking pointless things, Sasori sure does do alot of them. For instance, right before he died he gave Sakura information on where to meet with a spy he had planted amongst his former partner Orochimaru's people. Even before dying he stated that it was pointless.
19. Sasori says that his biggest regret is that he was stuck in a limbo. He wasn't fully human, and he wasn't fully puppet. If only he could completely be one or the other. I think it'd be funny to see what would happen if he some how was turned back human. *hint hint*
20. Sasori's death is speculated to actually have been a suicide. He died by being pierced through the cylinder by his very first puppets (his mother and father) controlled by his grandmother. His grandmother Chiyo said that for some reason Sasori intentionally did not avoid the blow despite the fact that he could have easily avoided it.
TWO MORE THINGS I FORGOT!
21. Chiyo had created a technique that would restore life to a dead person or a puppet by giving a living person's life to the dead. Chiyo had made this technique for Sasori. He looked a little stunned when she told him this, but then told her it was pointless. Sasori then died and Chiyo ended up using the technique on the current kazekage that had been kidnapped and killed. She died after using the technique.
22. Sasori's most feared puppet was one of the past Kazekage's that he'd kidnapped and killed about the same time he disappeared from Suna. This puppet had a frightening magnetic technique utilizing iron sand. It could take numerous different forms and Sasori mixed his poison in with the iron sand making it even more deadly than when the man had used it while alive.
AND FOR THE RECORD! Sasori doesn't have any of his puppets any more due to the fact that Sakura and Chiyo crushed them all. He's not happy about this.
I'm done! lol