How do you market to a toddler?

Apparently, I do not understand the secrets of marketing to toddlers. My husband is in dental school and we have started receiving lots of dental products. Last week, it was a crayola toothbrush. I thought this was kind of a silly idea. A toothbrush that looks like a marker? I'm not buying it... but I was wrong. My 18 month old son has been refusing to brush his teeth, but ever since we got this toothbrush, he carts it around with him and wants to brush several times a day. I had no idea he would be so gullable. I'll keep that in mind from now on.