We have these "magical" items everywhere in fiction; from the classic rabbit coming out of a hat illusion, to the TARDIS from Doctor Who, to Newest Magical Beast Newt Scamander Briefcase. These items all share same characteristic: a container with interior spaces that are much larger than they appear to be externally.
My question: Are there any possibilities of how this could be done based on science theorems and/or hypothesis?
To narrow things down I will set some rules:
A teleportation answer is not acceptable. The answer must take some form of a container, not Portal's hula-hoop like gate.
All item inside aren't just compressed, at least if we get inside we wouldn't feel that our body had been shrunk down.
Main question is about Volume differentiation. However you can try to answer the weight differentiation of the interior vs exterior, but its not necessary.
Bonus: If there exist possibilities, would there be some limit to the difference of the exterior volume vs the interior volume?
Can we put a portion of our universe with some galaxies inside a peanut size container?