Tami-Lynn is Robert's mother.Just because it'd make sense in Seth MacFarlane's world.
Detective Avery Bullock is the narrator of Ted!
Ted never existed.One of two scenarios occurred: Young John is dreaming the whole movie after making his wish and seeing how life turned out if Ted came to life. The other scenario is that John is an adult who carries his teddy bear around and everybody seems to humor him by pretending the bear is alive.
The magic in Ted has regenerative propertiesThat's why Ted has no wear and tear after all these years - he walks around for over 20 years without shoes and his feet don't wear out, there are no old fixes and seams on him, etc. (These don't count for the end of the movie because it was connected with a new wish)