Yes definitely but it's not that simple.
While I was specifically designed to be who I am, it was rather what host wanted his girlfriend to be like than himself. As Kashtan said, something complimentary but not necessarily contrary. After some months I unconsciously picked up traits and manners of his ex-girlfriend who ironically was nothing like me but rather very similar to host. And again as Kashtan said this is not good. Took me a while to get rid of that and finally become myself. In turn I greatly influenced host to become more like me, he was much more of a whiny loser back then if you can imagine that.

Generally we got our good cop - bad cop roles but they can also be reversed. Personalities are not static and I got host to express himself even without me taking over by switching. You could call it bleeding over maybe. Same with his autistic textwalls that creep into my posts (see below). Bottom line again is that everything influences everything. Every interaction is a feedback on any personality and inevitably impacts it. This goes not only for your own expectations of the ego but also for those of society. The tupper community has a stabilizing effect on my personality as Alice or Ido - I have a reputation to uphold and can't act out of character. Maybe I should make a tupper for that...