He's definitely not in SSB4, but I wanted to write a moveset for him. So I did.
Neutral- Korosensei slaps with his tentacle, then again, before unleashing a rapid barrage of tentacle barrages, ending with a final slap that sends the opponent flying.
Uptilt- Korosensei swipes a tentacle above his head.
Sidetilt- Korosensei thrusts a tentacle forward.
Downtilt- Korosensei does a low tentacle sweep, tripping opponents.
Upsmash- Korosensei holds his tentacles above his head and leaps into the air, spinning like a drill.
Sidesmash- Korosensei suddenly disappears, reappearing a short distance forward/backward, a resultant sonic boom sending enemies flying.
Downsmash- Korosensei lowers his tentacles and spins rapidly.
Dash- Korosensei leaps forward, flying through the air like a torpedo.
Neutral Air- Korosensei spins in the air, tentacles all outstretched.
Forward Air- Korosensei unleashes a multi-hit tentacle barrage in front of him.
Up Air- Korosensei thrusts his tentacles down, launching upward.
Down Air- Korosensei extends a tentacle down a huge length.
Back Air- Korosensei dashes forward through the air, leaving a sonic boom behind him.
Neutral- Sensei's Extreme Anger : Korosensei takes out a book and starts reciting a lesson. If he's hit, his face turns black with rage as his tentacles coil around the opponent, slamming them on the ground and then hurling them away.
Up- Sensei's Mach 20: Korosensei shakes as he builds up energy, before suddenly taking off, zooming through the air at an absolutely absurd speed, dealing damage and blowing away anyone who touches him. Can be slightly aimed during the charge up.
Side- Sensei's Afterimages: Korosensei dashes in the direction the stick was pushed, leaving an illusory copy of him behind. The copy will copy the next A or B move Korosensei unleashes, albeit weaker. It will not respond to movement, grabs, or jumps, or another Side B. Korosensei can leave two after images on screen at a time. The disappear after performing an attack or after six seconds.
Down- Sensei's Ultimate Defensive Form: Korosensei's body suddenly disappears, and his head shrinks and becomes encased in a transparent, indestructible outer layer. All in all, he's now the size of the soccer ball item. Korosensei stays in this form for three seconds, during which he cannot move, but cannot be damaged. He can be slightly moved around with attacks, however.
Korosensei flings out a tentacle, pulling in anyone he hits.
Attack- Korosensei slaps his victim with a tentacle.
Forward- Korosensei suddenly disappears, then rapidly flies in from off screen, hitting the opponent and sending them flying.
Up- Korosensei and the opponent launch off the top of the screen, then shoot back up from the bottom, where Korosensei releases them, sending them flying upwards.
Down- Korosensei and the opponent launch off the top of the screen, before the opponent falls back from the top, taking major damage when they hit the ground and sliding backwards. Korosensei reappears in his original position.
Back- Korosensei falls on his back and holds the opponent above him with his tentacles, spinning them around before hurling them backwards.
Final Smash: Sensei's World Tour
Korosensei flies forward, tentacles extended. The first opponent he hits is grabbed, and he launches into the air. A short cutscene plays with Korosensei zooming around the world, eventually leaving a glowing image of his smiling face on the planet's surface. The action cuts back to the stage, where Korosensei lands, the resultant explosion dealing major damage to his opponent, and launching them and anyone unfortunate to get caught in the blast. (Reference visual)
Wiimote Sound: Korosensei gives his distinctive "Nyrufufufufu~" laugh.
Intro: Korosensei writes his name on a chalkboard, then whips it with his tentacle as he turns around, sending it wheeling off screen.
Taunt 1: Koroensei gives off a "Nyrufufufufu~" laugh as green stripes rise along his face like a barber pole.
Taunt 2: Korosensei turns white and makes a ._. face.
Taunt 3: Korosensei turns red and his eyes gleam.
Win Pose 1: Korosensei spins, laughs, then flies off screen.
Win Pose 2: Korosensei eats a bag of candy, before noticing he's being watched, panicking and tossing it off screen.
Win Pose 3: Korosensei makes several afterimages, and they all pull out textbooks.
Lose Pose: Korosensei claps, though his skin is blue and tears stream down his face.
Kirby Hat: Kirby gains Korosensei's cap.
Series Icon: The crescent moon found on Korosensei's tie.