I dunno. Maybe it's because Great Snail Race came out when I was a little kid, and I had two or three pet cats, and it showed Gary graphically exploding on-screen? We've seen Spongebob act incredibly oblivious and stupid, but I can't think of any episode, before or since, that's portrayed him as being genuinely selfishly abusive. In A Pal for Gary he was well-intentioned and trying to do the right thing, which is in-character for him. In Great Snail Race, he abused his beloved pet just for the sake of one-upping his neighbor. Yeah he apologized, but it still leaves a bad taste in my mouth.