you clean him
wrap him up some presents
be glad that he finally has an acceptable substitute for his favorite cousin's lion
make him his own train book featuring him (you need a ninja dad for this)
covet his flexibility as he watches his new train come through the tunnel
honk with him
and finally tear him away amidst screams and protests to blow out candles on a cake he will scorn in favor of a bit of ice cream and returning to his train, all while you love him and cherish him and look forward to his next year.