Did he just eat a crayon or a box of crayons?
What breed of dog is this? the weight?
Thank you for that information. He may get an upset stomach but nothing more and you should watch for him to pass it safely. Pups get into a lot of stuff, that's their nature so I am going to direct you to a site of non toxic items pups tend to get into. Print off the list and keep it in a draw to refer to it in the future. Wishing you many happy years with your pup:)