Great post! I thought I replied right away when I first saw it, but I guess it didn't go through. Anyway, three thoughts in response...
I never thought of fall especially for tickling. Spring and summer's obvious reasons as you mentioned, and winter inspiring snuggling, make them equal contenders. But you're right that fall's coziness is perfect! It's my favorite season overall, and here when the air finally cools I definitely tickle my wife more.
Second, Halloween. Hell yeah!! Off the charts for sexiness, fun, playfulness, naughtiness... rife with temptations and opportunities to tickle.
Last but not least, tickling Kim Possible? Are you kidding me? OMG your wife is awesome and you are one lucky guy!!!