In one strip, Calvin has spent his whole allowance and wants a grenade launcher. He goes to his mom and asks when it will be christmas, and she answers, "Not for a long time." He then asks when his birthday is, and she again says, "Not for a long time.". Finally, he asks when his allowance is, and she says, "You spent it already." Calvin then sells the car with a sale stand. Although we really don't know the first time it happened, Calvin's dad mentions that "He blew it again, dear", implying that he has sold the car before.