In it, Calvin appears to have been prescribed Attention Deficit Disorder drugs ( a contentious point in America, where many unruly or hyperactive children seem to be prescribed them as a matter of course. The commonly-perceived effect of ADD drugs is that they leech a child of any character or enthusiasm about the world). Then, at the end, as Calvin has stopped imagining, Hobbes in effect dies, and becomes just a stuffed toy again. Many people have read a broader meaning into it beyond that of it being purely a comment on ADD drugs: that the loss of our imaginations and belief in the endless possibilities of the world is an inevitable part of crossing from childhood into adulthood.
It is the saddest comic strip ever.
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