The Murderhorn is stated to be over four miles (21,120 feet) in height. This is taller than Mount McKinley, which is the biggest mountain in the United States. This is likely an intentional joke continuing the running gag of Springfield having impossible geography.
In the flashback, the can of flapjacks seems to be rested on McAllister's foot, yet it is drawn totally flat as if it is on the ground.
When the Sherpas were dragging Homer up the mountain, we see his blue jeans come off revealing beige thermal warmers underneath them. The thermal warmers then come loose revealing Homer's underwear. Homer then wakes up and realizes he is being dragged up the mountain. When he stands up we see him in his underwear and pulling up only his blue jeans; the beige thermal warmers weren't anywhere to be seen.
When Grampa's teeth fall out of his mouth, they perfectly fit McAllister's bite wound, revealing it was Grampa that tried to take a bite out of him, just as McAllister had recorded in his journal. However, Grampa was a young man at the time and would have had his regular teeth, not dentures; therefore they should not perfectly fit the wound like this.