We're kind of obsessed with constellation designs around here - we want them on everything. So we came up with an easy way to embellish baby onesies with a cosmic design, by simply dotting them with a Clorox Bleach Pen in a starry pattern. The Big Dipper on the onesie on the left, and a random spattering of stars on the right.
Slide cardboard or an old magazine between the two layers of the garment you're working on and dot the bleach pen in any design you choose. I started with different sized dots, but got brave and moved to a criss-cross star. The pen doesn't offer a ton of fine-tipped control, so simple designs like dots are definitely the most successful.
Leave the design for 15-20 minutes, then rinse off the bleach and wash and dry the garment as recommended.
My attempt was actually unsuccessful on the shirt shown in these how-to photos - the tee shirt was a very soft, lose weave (and a tri-blend), and the bleach bled so that the stars came out as blobs. In the black tee and blue onesie shown at top and below, the weave was tighter (and 100% cotton), so the bleach didn't bleed and they held the design better. So definitely test the pen on a small part of whatever you want to design.