The claim was not “made up” by one single person in any clean, provable way; it appears to have spread as an early 9/11 conspiracy narrative tied to antisemitic rumors and reused in later forums, fliers, and videos. A mainstream fact-checking/reporting trail shows the broader “celebration” story was false or unsupported, and the “dancing Israelis” angle was later amplified by conspiracy sites and social-media circles rather than established evidence.

What the record shows

  • The “dancing Israelis” story refers to a group of Israelis arrested on 9/11, which later became fodder for claims that Israelis were behind the attacks.
  • BBC notes that 9/11 conspiracy theories started appearing online within hours of the attacks and then spread widely over time.
  • A 2019 anti-Semitic flyer campaign reused the claim that “Israelis were seen dancing” at the Twin Towers site, showing how the rumor kept circulating years later.

Who is usually associated with spreading it

  • The claim is most strongly associated with anonymous internet posters, conspiracy forums, and anti-Israel/antisemitic propagandists , not a single identifiable original author.
  • Later outlets and commentators amplified it, including conspiracy-focused video and article circulation online.

Important nuance

  • There is a real, documented incident involving Israeli men who were detained that day, but that is not evidence that they were involved in planning or celebrating the attacks.
  • The jump from a disputed incident to a claim about foreknowledge or orchestration is part of the conspiracy narrative, not established fact.

TL;DR: no single clear originator is established; the claim spread through early post-9/11 conspiracy spaces and was later recycled by antisemitic and conspiratorial sources.