Throw it in revers(ible)

My kids think reversible shirts are magical and, after making a few, I'm inclined to agree!

When I first started sewing, I thought "I'll just make two shirts, sew them together, and turn them right side out!" (It did not go well.) 

There are many reasons you may want a reversible shirt. They're thicker than regular shirts, so you can make what amounts to a sweatshirt with only medium or light-weight fabric. There are no scratchy seams. You can reverse it if, say, you spilled chocolate ice cream on your shirt while you were eating lunch at Red Robin right before a meeting and you didnt' have time to go home and... oh... too specific? 

There is a simple trick to getting shirts to be reversible with the seams entirely inside of the garment, but it's hard to explain. I'll let one-year-ago-me explain.