What episode soes sanji join the crew in one piece?

Answer 1

Well, it's a long story, but pretty much this sums it up:

1. Zoro was on a journey (to become the best swordsman in the world)
2. When he arrived, a girl, Rika, was attacked by Helmeppo's, the spoiled son of the corrupted Marine captain Axe-Hand Morgan, pet wolf.
3. Zoro saved her by killing the wolf
4. Zoro was arrested and Helmeppo made a deal with him: if Zoro could survive a month without food, he would be pardoned.
5. Enter Luffy and Koby
6. Luffy asks Zoro to join him
7. Zoro refuses
8. Rika tells Luffy about the situation Zoro is in
9. Luffy makes Helmeppo mad
10. Fighting ensues (Luffy and Zoro fight Helmeppo and his father)
11. Helmeppo is defeated and his father arrested
12. Pretty much after that, Zoro joins Luffy's crew.

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Answer 2

I can't answer that question fully, so I am just going to tell you one thing: the episode in which the whole Don Krieg thing started, or, you could say, when Sanji first appeared, not necessarily to the Straw Hats.

He appeared in Episode no: 20. I am not sure which Chapter he appeared in the Manga.

Answer 3

Around episode 30 when Luffy defeats Don Krieg.