And your second thought is to take a picture of it . . .
Naturally the third thought was the answer to my first "Evan hasn't been around playing with crayons long enough, that's why this hasn't happened in the last 6.5 years!"
Followed by the logical action of googling "removing melted crayon from a heat register" only to find that you are more fortunate than most who apparently have that shit melted on carpet! Some steel wool took care of it for me :)