I was watching this episode on tape the other day. As a kid, and even still to this day, it always struck me that this episode was kind of "dark" compared to the rest of the series, though I have to wonder if it was intentional, to sort of send the message of why not to disobey your parents when they tell you not to go somewhere: the whole scene at the dump played out in a rather unnerving manner, between the troublesome music scoring that was used, D.W.'s constant wailing in fear for her brother, and Arthur's near blood-curdling scream as he cut his knee. Even their arrival home seemed to play up a slight "dark" tone as well, between Arthur and D.W. basically sneaking into their own home, and Arthur's moaning every time he moved his knee, which caused D.W. to gasp in worry.
I also have to wonder though, looking at it as an adult, if perhaps the lima bean can aspect might have been exaggerated just a bit; I'm all too familiar with how sharp the edge of can lids can be, but would Arthur bumping his knee up against do as much damage as it did? I mean considering he was wearing his blue jeans, and denim seems to be a rather study and durable fabric. I'm not saying it's entirely impossible, I've had to wade my way through briars and thorns before while wearing long pants and I still had pin-hole punctures in my skin, but I wonder if a thicker and stronger fabric like denim wouldn't have at least spared Arthur that much damage to his knee.
I will say this though, I LOVE the intro with all of Arthur's various different organs, all wearing his glasses and evetrything.