Thank you for the birthday wishes. My parent's are good to me.
The place my parents got the cake from, you can bring in a picture, and they'll put it on the cake. It is icing, so it is fully edible. I have no clue how they do it.
Spark plug candles? That's be awesome. I may have to look into that for my dad's birthday. I know he would get a kick out of it. Other than that, we usually just use numeric candles now. Individual ones are a little to messy.
Here's what my parent's did last year. It's awesome what can be done. I printed this out before I bought my cobalt (had the exterior of the car on the outside, than unfolded it to see the interior), and my parent's brought it in, and the place put it on the cake some how.
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Hahaha. Look what I found. Shipping is definitely pricey.