Elliot must have learned about Martin Luther King in preschool because I overheard him explaining the holiday to his sister: "He was a really good guy who made everything fair, and it's his birthday so Mommy and Daddy don't have to work."
I suppose someone who "makes things fair" is the perfect hero for 4-year-olds, since they spend so much time complaining when things are not fair.
Of course, MLK fought true injustice. Elliot's version of unfairness is not being allowed to turn the couch into a fort.
Maybe we can explain the holiday with a little more nuance next year.