The Dunder Mifflin shorts are definitely my fave, even if they make me a bit sad that The Office has ended for good ;) We will keep the Dundy spirit alive through sewing, haha!
First, obviously, you need some t-shirts. Casey generally wears a size L. The bigger your shirt, the bigger child you can make these for. This will probably be the last year I can squeeze Kelby shorts of the Large shirts, but I can always buy bigger tees from the thrift store. He wears a size 5 currently, if that gives you a frame of reference for what size shirts to use for what size kids. If you have a toddler still, you could probably make pants this way!
Next, pin your shorts front and back piece onto your t-shirt any way that it fits. I put mine on a bit of a diagonal and I actually really like how the logo twists around from the front to the toosh. You can see in the bottom right corner that the top of my pattern piece goes onto the sleeve seam a little, but no matter, those lines will disappear into the seams and casing.
Next, just follow your directions for putting the shorts together. I use 1" elastic in mine and I used yellow thread for a cute contrast.
I like to put a tag in the back of my kids' pants, shorts and skirts, just so they know which way is the right way. I just put a folded piece of ribbon into the casing before I sew up my elastic hole.
Next up, the shirt. Just as easy and no pattern required :)
And you're done!
For this next pair, the yellow t-shirt actually had ribbing around the sleeve hems, so I cut that off (leaving about 1/2" of the t-shirt part for a seam allowance) and reapplied it to the arm holes and top stitched it.