What does "It could not be less arbitrary," and "Alice through the looking glass" mean?


Sheldon: Look at Planck's Constant. People say it's arbitrary. It could not be less arbitrary. If it varied even slightly, life as we know it would not exist. Bam! Now, now, let's reconsider the entire argument, but with entropy reversed and effect preceding cause, so you are thinking of a universe that's not expanding from the centre, no, it is retreating from a, from a possibility space. Bam! This is a space where we are all essentially Alice through the looking glass, standing in front the Red Queen*, and we're being offered a cracker to quench our thirst.

"It could not be less (arbitrary)" is a hyperbole used to say that something either isn't (arbitrary), or is the worst example of being (arbitrary) because it is the least (arbitrary). So Sheldon is saying, "People say it's arbitrary, but it is definitely not arbitrary, since it is the least arbitrary thing."

"Alice through the looking glass" is a reference to the books "Alice's adventures in wonderland" and "through the looking glass". Unfortunately, I haven't read these, so I can't say for sure what he's trying to say. If I guessed, it's something like, "In this example, we are like Alice, entering a mysterious and strange world that we don't understand, a world that contains logic that we don't understand".