Which episode in sonic does tails get kidnapped?

Well, darling, Tails gets himself into more trouble than a cat in a room full of rocking chairs, but if you're talking about the episode where he gets kidnapped, that would be in the "Sonic X" series, Season 2, Episode 9 titled "The Beginning of the End." Tails may be a whiz with gadgets, but sometimes he needs a little rescuing himself.