This is for modern Disney Store brand male dolls. It's an exact reproduction of some Naveen pants that discolored NRFB, so I took them apart to copy them. I believe most of the male dolls use this same cut.
Getting Started
Choose any fabric you like, use a little patch of velcro in back to close it. The manufacturer put a line of fabric glue along the inside edges. I recommend a fine tip wash-away marker for exact markings.
Here's the fabric grain of the original pants, it's more or less parallel/at a 90 degree angle to the bottom cuff.
Click on the thumbnail to enlarge it.
Trace the pattern on the wrong side and cut it down exactly on the line.
Trim down the pattern to the inner edge, then trace that onto the fabric.
Now you have the most accurate pants pattern possible.
Do both pieces.
Add a line of Fray Check or some fabric glue to prevent it from fraying apart later. Let that dry.
Put the crotch right side to right side, sew up the front and back crotch.
Turn the pants right side out. Fold the cuffs and waistband over on the line, iron it. Iron quickly so the marker doesn't get scorched. Topstitch those down.
Turn the pants inside out. Sew up the inseam.
Turn the pants right side out. The top flap is on your right side. Fold it over on the line, iron it, and topstitch it. I added two lines of stay stitching on the bottom flap just to be safe.
Last, sew on the velcro. Don't forget to wash the marker out and press them.