When Jack realized Oogie Boogie has returned, he tells Sally about the evil.
Jack Skellington: LISTEN, SALLY! Oogie has returned!
Jack Skellington: Yes, it's the truth! An evil named Set has managed to resurrect him!
Sally: Oogie... A familiar enemy of ours...
Meanwhile, at the Halloween Town Square...
Mayor: It is with great distress that evil has returned in the form of Oogie Boogie, our nemesis!
Child: Not Oogie Boogie! He's so mean!
Dr. Finkelstein: Yes, AND IT'S THE OLD TRUTH! And I have proof! Read it.
Clown: Very evil indeed. What should we do now?
Jack Skellington: We must head to Christmas Town, where we have the Conference of the Seven Kings. COME ON!
Meanwhile, Jack returns to Christmas Town, where Santy Claus welcomes him again.
Santy Claus: Seasons Greetings, Jack! How are you?
Jack Skellington: Fine, Claus.
Five minutes later in the conference...
Santy Claus: It's true that Oogie was resurrected.