Student or Learner
It's a pun on the phrase "out of shape". That means unfit, not having a good body shape, perhaps overweight.
So even though from the picture we can see that Mr Wilson can reasonably be described as "out of shape", the child takes the words "out of", which can mean that something has been finished, there is no more of it, and the word "shape", from that description and uses it to say that actually Mr Wilson's body exhibits many different shapes (one of which is "round" - my words, not from the cartoon).
So contrary to the statement "You are out of shape", meaning "Your body doesn't have any shape(s)", the boy says that his body has many shapes.
To be honest, it's not terribly funny but it's a reasonable play on words.