Long-sleeve onesie to Short-sleeve T-shirt

As the weather warmed and the girlie outgrew her winter clothes, I thought I'd try to make things stretch out a little longer. 

Before:

After:

An 18-month long-sleeve onesie has been remodeled into a 3T t-shirt, inspired by some ideas from the blog of a much more talented seamstress than I .  Here's how:

Cut the sleeves and bottom off of the longsleeve onesie, taking into account a 1/4" seam allowance on the sleeve length.

Cut the cuffs off the sleeves, again allowing for a 1/4" seam allowance, and save.  Cut along the seam of the remaining tube of sleeve fabric to open it up into a rectangle.  Cut this into strips of fabric (7/8" inch looked good to me; you can use whatever width strikes your fancy).

Sew a basting stitch down the center of these strips, overlapping about 1/4" between adjacent strips, until you have a long piece about twice the circumference of the bottom edge of the shirt.

Gather into uniform ruffles and sew onto the bottom edge of the t-shirt with a narrow zig-zag stitch so the seam will stretch a little with the knit fabric:

For the sleeves, take the cut-off cuffs and pin to the sleeve edge, right sides facing and raw edges together.  Since the cuffs are narrower than the short sleeve edge, you'll have to stretch it out to fit it evenly all the way around.

Sew in place with a narrow zig-zag stitch to give it a bit more stretch.  Flip the cuff right side out, and you've got a finished sleeve!  Steam iron the edges towards the sleeve.  For instructions on a cuff using an unfinished strip of cloth, check out Make It and Love It where I got some of my ideas.

Here's a slightly different take on the bottom ruffle, this one gathered and sewn on one edge, and then topstitched.