Sonny liked being short.
Sure, it was no fun when Pete used his head as an armrest, but there were quite a few perks to being short.
For one, nobody notices you when you're eight years old and you look short enough to be five. You can slip past anyone without being noticed because you're not five, you're eight, so you know how to be sneaky. You can still get a free ice cream from Mr. Softee because you're not taller than the panting of the ice cream cone. Then you can give the piragua guy those big, innocent eyes and get a piragua for free too.
But Sonny's favorite part of being short is when he sneaks packages of Ramen noodles from the bodega. He can run down the aisles without getting noticed, stick the package of noodles in his pocket, and sneak back out without Usnavi or his aunt and uncle noticing. Then he can go find Pete, and they can make the noodles together. Because Pete's eleven, so he knows how to use the stove.
And he can reach all the buttons too, which is a plus.