There is no season 9, and current addition of s09e21 (Joker for a Day: Part 2) is a Special, as listed on TruTV.com:
https://www.trutv.com/full-episodes/impractical-jokers/index.html
Every once in a while, new episodes to this show appear as the latest episode of season 8, but in season 9. To the best of my knowledge, season 9 has not been announced, but the group is currently guest hosting on Misery Index (correlation is not causation, I know).
