Henry saw a "Charlie and Lola" episode one morning in which Charlie dresses up like a monster.
This means, of course, that Henry cannot finish the episode and must commence creating his own monster costume. Here is version #1:
And version #13:
He decided the Batman costume was much more scary than paper bags, and the claws sculpted from card stock were "absolutely ferocious."
The pie pan stuck through the batman ear things I cannot explain, nor the mustache fangs or kneepads on the upper arms.
You'll have to ask to the monster.