Find some old shirts that you no longer wear or are headed to the trash.
Use an existing pair of shorts as a pattern.
Fold the shorts in half and line up the outer edge along the bottom hem and side edge of your shirt, like so.
Adding a 1/2 to 3/4 of an inch for seam allowance and another inch for the waistband, trace around the shorts, using both sides of your shirt for the front and back of the new shorts.
Cut out your pieces.
Open them up and lay them together, right sides facing in.
Pin along the edges, making sure the bottom edges line up.
Leave the straight bottom edge unpinned and unsewn.
Sew along the pinned edges. You should now have this.
Now line up the legs and crotch of you shorts, again, lining up the bottom edges.
Sew.
Now you can fold over the top for a waistband, being sure you make it large enough for your elastic. Pin and sew, leaving a 2 or 3 inch gap for adding elastic.
Cut the length of elastic needed, then run the elastic through the waistband.
Sew the gap closed and you are done! No serging (since jersey won't fray) and no bottom hem since you used the existing one. Yay for shortcuts!
For a shirt, I picked up a pack of basic tees.
And quickly added an applique. A race car and a rocket. Very boy-esque. For a how to on fabric appliques go here.
I matched the shorts up with a tee and they're good to go!
Each pj set came to $1, for the price of the t-shirt. Everything else I had. What a bargain!