I remembered that I owned an old cotton flannel night shirt from Mervyns that I think I "borrowed" from my mom when I was a kid (and never gave back). I had worn the poor thing absolutely to the bare threads; it's how much I loved it. It was falling apart. I think one more washing would have ended it for good.
I wanted to recreate the general look and feel of it, but I didn't want to have the pockets or the buttons.
So, I traced out the relative dimension of it on my pattern paper. The garment was simple: Front, Back, Sleeves, and Facings. Everything is fairly "oversized" (four inches of ease) so I didn't have to worry about fitting the garment to my specific measurements. And even the sleeves had no easing. (I hate easing sleeves.)
It was a nice change of pace. Here's the night shirt laid out on the dining room table. I traced around each piece, then added a generous seam allowance. I used a V-neck opening to make things simple. This is probably the simplest pattern I've recreated.
I even had a helper who supervised my drawing and cutting out the pattern.
This time, I did make a mock-up of my pattern (as it was not tried and tested). And I made a few adjustments in different places. I marked locations for a "long" and "short" night shirt. I made two: one in read and the other in the plaid. I also did some stylistic variations between the two. It only took about 2.5 yards of the fabric with plenty of fabric left over.
Now, DH wants one too. I test drove the red one for a few days. And me tell you, these are really comfy! I need to make more.