All Hell Breaks Loose: Part 1 - S2-E21
Factual error: Dean finds a body in the house that burned down. The arm has a metal watch still on the wrist with hardly any damage. It has some black soot on it but that's it.
Suggested correction: Your entry is based on opinion/theory only. It's possible for someone who died in a fire to have parts of their body to not be affected by the fire.