Leon hadn't carved pumpkins, or did anything to celebrate a holiday besides passing out candy, since he was very young. For one, it was kinda lame to just do it yourself. That would just remind him of his loneliness. And well, he used his free time to sleep.
But now he was dating you, someone who celebrated every single holiday to the max. So far, he's celebrated Thanksgiving, Christmas AND Hanukkah, New Years, Valentine's day, Easter, and Cinco De Mayo. Now Halloween was pretty much the only one left on the list.
He was working while you decorated your house but you made sure to leave some pumpkins for you two to carve. So after a day of much needed rest, he went to your place one night. And you already had the pumpkins set up and ready to be carved on your living room floor when he walked in.