Meet Sam. A little guy, he comes into the room riding a dog-like creature and holding a sign that says "I am Sam" (1). Smiling, he tips his red Seven Dwarves-style hat. (No, he's not Dopey.)
Monstrous, massive, hugely important note: The only actual text here is what we just quoted you. Everything else we're inferring (figuring out in our genius brains) from the illustrations. Yep, that's how good the illustrations are. We'll use them quite a bit in our summary.
Sam rides past a not-so-little guy (we call him the big guy) who's sitting reading some papers with part of the alphabet printed on them. Newspapers, perhaps?
The big guy doesn't look like he's happy to see Sam pass by. Come on, big guy. We know it's irritating when people disrupt your reading, but give Sam a chance.
Sam comes back, this time riding a big pink creature and holding a different sign. This one says "Sam I am" (3). Fancy.
In what looks like anger and exasperation, the big guy throws his papers on the ground.
With one fist clenched, he says, "That Sam-I-am!/ That Sam-I-am!/ I do not like/ that Sam-I-am!" (4-7). Angry much?