1. He was dead the whole time
  2. The dude in the room isn't dead!
  3. It's a sled
  4. It's people!
  5. He's a super hero
  6. They're the same person
  7. He's Keyser Söze and basically just bullshitted the detective the entire time
  8. He's Luke's dad
  9. His mom is dead and it's just him in a dress cuz he's a psycho
  10. He's only gonna be dead for three days and then he'll come back and ascend to Heaven and judge you
  11. It's Earth
  12. He's mental, not a genius
  13. He has a twin brother