My theory on what’s in the box and the mimic
So it’s five things that become one right?
I always thought it would be one of each thing represented an Afton family member one for crying child one for Michael one for Elizabeth one for William and one for Mrs.Afton five things become one because five Aftons made the afton family
Five things are destroyed/killed then put back together into one
Crying child is killed
Elizabeth is killed
Michael is killed
William is killed
Mrs.Afton MIA (presumably dead)
“You are broken let me put you back together” is something always brought up for crying child and why William went crazy
But
What if down the line someone is going to try to reunite or combine the Aftons like the kittens in the candy cadet story
The mimic sets up that dinner scene in ruin and the whole mimics backstory is the mimic being their to replace or mimic the dead to keep the family whole and it going horribly
Maybe Mrs.Afton is trying to rebuild her family and what’s in the box are items she will use to help train memories in the mimic or mimics (unless she believes William was guilty she’d probably want to bring him back too) this is probably why the pizzaplex is built on the original location
If we really wanted to make it more complicated then maybe
Mrs.afton isnt even an Afton maybe she’s a Murray (kept her maiden name)
or Fiona is Williams sister (Fiona wears purple which typically is used to reference William)
Either way she needs to know about the mimic and know what it’s capable of