Kirby: Right Back at Ya! has 100 episodes in its main anime series. The Japanese series aired from October 6, 2001, to September 27, 2003, following Kirby’s adventures in and around Cappy Town as he battles monsters sent by Nightmare Enterprises.
The series is divided into four seasons: 26 episodes in the first, 25 in the second, 25 in the third, and 24 in the fourth. Together, those seasons total 100 regular episodes. The final numbered episode concludes Kirby’s battle with Nightmare and the threat to Dream Land.
A common source of confusion is a later short episode. An eight-minute Kirby anime short was released separately and is sometimes listed as episode 101. It was originally shown as a 4D feature in Japan and later distributed internationally through Nintendo Video. That short is not part of the original 100-episode television run, so 100 is the standard answer for the anime series.