This item of baby cuteness has been on my to-do list for ages now.
All my babies have slept in a sleeping bag from about 6 months old until they are old enough to wake from bed in the morning and need to walk to our room, about 2 years.
They do several things: comfort (once they are strong enough to wriggle free from a swaddling blanket); stop them kicking their blankets off and getting cold; signal bedtime. I swear by them and have so far been using a cotton go go bag by merinokids.co.nz
Heading into winter here, I wanted a lined wool one for Adelaide. The outer layer was a really ugly wool skirt made of the softest merino wool knit fabric, wrap-around style with two panels crossing at the front. I just kept two panels to make the bottom of the sleeping bag and used a simple bodice pattern to create the top. Lining it was a problem only because I had it all wrong in my head and forgot to sew it as an open garment, instead I fiddled around with a closed neck and only one side opening, which closes with a zip.