Jacket 'o Pain?

Why is it that getting dressed (or undressed) is a time of glee and jubliation for Colin, but if I try to put a jacket on him... any jacket... he immediately dissolves into tears and squirms as if he's being tortured?  It is so bad I started checking both of his coats to see if there was a pin, railroad spike or perhaps a flame-thrower hidden in one of the sleeves.  Thus far I have been unable to determine the cause of his outrage.

Just another one of the great mysteries.  Construction of the pyramids.  Easter Island.  And the jacket-o-pain.