Over 66 ads, the Mac and PC are contrasted in every way possible: creativity vs routine, play vs work, security vs viruses, compatibility vs incompatibility.... the list goes on.
Ironically, in the context of the campaign, the PC is actually the funnier, more entertaining character.
The creative team could see this, and they had to be very careful not to overplay their hand and reject PC too much, in case it made the audience resent Apple and sympathise with PC.
"The writing wasn't easy. The whole "Mac vs. PC" thing, it turned out, was tricky. And could easily backfire if "confident and capable versus insecure and flawed" read more like "smart versus stupid"—or worse, "smug versus lovably inept." The nuances of tone would be everything."
(From an account of the creation of the campaign.)