I got that idea when I have watched The Shower MV where three IUs are singing together!
But I became 100% sure about it when I saw a Chinese tiktoker who looks EXACTLY like IU. I bet that girl escaped from IU producing factory and started her new life in China, like in the movie "The Island" (2005)
Also if you think about that: IU is the most popular singer, a wonderful actresss, a highly acclaimed songwriter and producer, a famous philanthrope, a dancer... How can a single person handle it? Nohow! There are simply multiple IUs
Other evidences:
1) IU is going to release her new MV next Wednesday where she plays a celebrity who finds a girl that looks exactly like IU and IU is trying to catch her!
2) There is a video where another three IU's are singing Blueming's fan chant
3) There is a video where IU takes interview with IU
4) IU's agency has a part-time worker, Lee Ji-Dong, who is VERY similar to IU
5) IU's agency is called EDAM Entertainment:
-- EDAM
-> EDEN
-> The garden of Eden from the Bible where the first humen were living
-> EDAM is the company where the first clones are working
