Recently a family member asked me to make something for their daughter... They sent me a reference shot showing the buttons/collar and red...
Pattern: Straight Grain's Bubble Dress with Little Lizard King's Sunsuit pattern.
Fabric: White woven fabric I had laying around for the collar, super soft red cotton lawn for body from Spotlight.
Buttons: Vintage score from a second hand store.
Elastic: 1" elastic for back. Underwear elastic for around legs (makes life so much easier then encasing it)