Okay, yes, I understand about his current condition. I guess, when I fantasize about tickling him - I think of him more in the mid-80s. Although, I did write a story about Mike Flaherty and Alex Keaton tickling each other's feet in 2000 - but they wouldn't have MJF's condition.
Since I'm supposed to cut back on mentioning MJF in every topic, I might as well post my views on the love/hate relationship on tickling in this topic:
For the longest time, I said that Marty McFly liked being tickled just about everywhere - except for on the soles of his feet. However, when he had to let his teacher tickle his feet as punishment for slacking on his classes - he was very reluctant to admit that he didn't completely hate having his soles tickled. The second time he let his girlfriend, Jennifer Parker, tickle his feet - he had to admit that there was something about being tickled there that became a turn on for him. So he eventually let Jennifer routinely tickle the soles of his feet.
As for Alex Keaton, I pretty much said the same of him. He told Ellen Reed that he hated having the soles of his feet tickled - because he was just too ticklish there. I didn't really have him mention that he loved being tickled elsewhere - but that's what I imagine. However, when he agreed to let Ellen tickle the soles of his feet if he lost a bet - he, too, realized that he didn't completely hate having the soles of his feet tickled. So it became a regular routine between him and Ellen - and his sister, Jennifer, soon got into the act too.
As for Michael J Fox himself, I never really had him say that he ever hated having the soles of his feet tickled. Although, he was very apprehensive of letting Tracy Pollan tickle his feet - when he lost a bet. As with the other two, Tracy eventually made it a regular routine to tickle the soles of MJF's feet.
I imagine that Marty McFly, Alex Keaton, and Michael J Fox would all be equally ticklish on the soles of their feet - as MJF have played the other two characters.