If I didn't already know that they can pip at different times before this week, I certainly would now.  
I started a bunch of bantam eggs a few days before setting the full-sized ones so that the little guys would have a 5 day head start and not be immediately out-sized, but when I went to move those to the hatcher, there were a few of the other eggs that seemed like they couldn't afford for their air cells to get much bigger and figured what the heck - try putting them in the hatcher with the super high humidity while they waited for their lockdown to start.  The last of those five eggs just hatched a few minutes ago.  A couple hatched yesterday.  
Meanwhile... their siblings still in the original incubator hadn't even pipped until last night.  
Now, 24 hours later, some of those on the close side of the incubator are starting to zip.  On the far side of the incubator... nothing.  It's like there's an invisible wall running down the middle.  That's the part that seems bizarre to me.