What is the meaning of ''Messy Room'' by Shel Silverstein?

This poem, like most by Shel Silverstein, is very fun and easy to read, with comic elements that keep the tone lighthearted.  The speaker in the poem is appalled at the state of someone’s room – “Whosever room this is should be ashamed!” he exclaims in the first line, and goes on to list all the ridiculous ways the room is out of order – nothing is in its place, and the mess is so bad that “his smelly old sock has been stuck to the wall.”  Imagine how many washes that sock has had to avoid to be able to adhere to the wall of this person’s room!  The speaker repeats the first line of the poem, to emphasize his repulsion at the sight, and goes on to try and discover the culprit, accusing others by name – “Donald or Robert or Willie or –“ but here he is interrupted, and told that the culprit is himself.  “Huh?  You say it’s mine?  Oh dear/I knew it looked familiar!”  The room was in such disarray that he didn’t even recognize it as being his own – it had ceased to be a collection of all his possessions and had instead morphed into an unrecognizable pile of junk, such was the extent of the mess. 

The moral here is one against hypocrisy – we should not be so quick to accuse others of wrongdoing or negligence when we ourselves are just as guilty of the same.  Similarly, we should not be so quick to accuse others when responsibility lies also with ourselves.