No matter what you call it, Jon Jon, longall or overall they are just to cute. They are easy to make and can be dolled up for all occasions. Snaps in the legs (for diaper changing) and buttons on the shoulders, you can't go wrong with this precious outfit. Here is a tutorial on how to make the Jon Jon part 1 and 2.
I used Childerns Corners Johnny Pattern. I like it because it is for skinny Kids.