I recently found this out about onesies. Did you know that the reason why they have that layered part at the neck is so that you can pull it down off the baby's body instead of pulling it up over their head in a case of a poopy explosion that gets all over their clothes?? I did not know when I had my first baby. It could have been very useful knowledge in one particular event.
It is the most memorable trip to Barnes & Noble that I ever took. Noah was a little over a month old and my friend came to Arizona because both of our husbands were deployed to Iraq at the time. We decided to go shopping, of course, and brought the little guy. We ended up at Barnes & Noble which ended up being our last stop because Noah had what we like to call an "assplosion". His onesie was full of it, it car seat was full of it...it was awful. There was no way possible that the stuff was not going to get on my hands, I just had to go for it to clean him up as well as the car seat. (BTW I'm pretty sure I pulled the onesie up over his head b/c I didn't know about the purpose of the layered neck). It was pretty much the exact moment I understood that you need to pack your diaper bag for the unexpected b/c I didn't bring him extra clothes. So we drove home with Noah in just his diaper and cleaned out car seat (as much as could get clean). Don't worry he got a bath right away!
The point of this story, is that onesie's are amazing in ways that you didn't even know. They aren't just cool because they have snappies at the crotch to easily access a diaper change.