Having done a few fanfic stories with Family Ties (even though Back to the Future is my main fandom), I realized how you pretty much have to pick and choose what you consider to be FT canon. The most obvious inconsistency, of course, is how Andy aged rapidly between seasons four and five. The only way to really explain that would be "magic", but seeing as magic is never in the series - you pretty much have to choose one or the other in your vision of the Famile Ties Universe. There have also been inconsistencies with Alex's age. He's seventeen at the beginning of the first season, but he doesn't turn eighteen until the middle of the second season. Then there are these episodes that don't seem to fit in with the rest of the series (like Greg being Alex's best friend).

So, how do you handle these continuity inconsistencies with the series - especially if you happen to write fanfic for the series?

Did Alex ever say that Greg was his best friend?

I don't know. I haven't seen the whole episode. For some time, I even had the names Doug and Greg mixed up. I think Skippy is the friend he's the closest to, though.