to be out of their minds
The German phrase 'aus ihren Kisten herauskommen' is the direct translation of 'get out of their boxes'. This phrase is used to encourage people to think outside the box or to try new things. It can be used in a variety of contexts, from encouraging creativity to promoting innovation.
The apples that come out of their boxes are always the best.
This phrase means that each of the better quality apples typically comes out of its box. It indirectly implies that things (in this case, apples) reveal their quality when they are taken out from their hidden places (the boxes).
I saw the children who come out of their boxes.
This phrase paints a picture of children playing, and probably using boxes as part of their play, imagery perhaps for children building makeshift hideouts using boxes, and then coming out of these 'hideouts'.
When will the books come out of their boxes?
This phrase could refer to someone anxiously awaiting the unpacking of boxes after a house move or organization of a library. It could also be asking about when a certain book will be taken out of storage or finally be used or read.