Prior to the beginning of the manga, Blue gave his Scizor, as a Scyther, to Chuck for intensive training. One of the skills it learned was reading its opponent's moves.
Blue's Scizor first makes its appearance as a Scyther in A Tale of Ninetales after Red and Blue accidentally switched teams after crashing into each other after which he stayed in Red's care for three days before being returned to his rightful Trainer.
During the attack on the Team Rocket base, Scyther was immediately sent out to attack Koga but was subdued by his Grimer shoulder armor and pinned to the ground. Blue attempted to use him again as a last ditch effort to defeat Koga but he was quickly countered by his Ekans and defeated.
Scizor, still a Scyther, makes brief but important key appearances in the early rounds of the Yellow chapter, where he was first sent out to battle Agatha and her Ghost-type Pokémon after her Gengar's Dream Eater wore off, allowing Blue to seize this opportunity to put his discipline to the test by having Scyther slice her gassy Gengar and Gastly to pieces. He thanks Evan, the young boy who was able to help him break out of the terrifying attack for this newfound ability (which he lacked when fighting another Gastly against Koga in the Pokémon Tower previously), giving him the Lapras he caught earlier in exchange.
After this flashback (which was told to Yellow), Blue uses Charizard's flames to set a boulder on fire for Scyther to train with.
He makes his first appearance in Forretress of Solitude as a Scizor where he was used to stop four Pokémon that started rampaging due to the radio signals caused by Team Rocket after which Blue soon captured. He wasn't seen for the rest of the chapter.
Scizor was first seen when Blue used him in an attempt to fight an Invisible Enemy but he was unable to land a hit on it. Blue also used him during his battle against Red to see who would earn the right to learn the Ultimate Moves. During the battle he managed to help defeat Snor, and defeated Gyara before being recalled while fighting Aero.
He later appeared again in Trainer Tower fighting against the Tower's computer, "R". He attempted to free Professor Oak from his captivity but couldn't due to an energy field and was shocked into submission along with the rest of Blue's team.
