Warning: This "fun fact" regarding City on the edge of forever may tear down the fourth wall of the Star Trek Universe. Proceed at your own discretion.
It is no secret that some of the Star Trek TOS episodes where filmed on the "40 acres" backlot of the Desilu Studios. On the same streets used by other Desilu produced television shows of the day. Two sites explore the making of these TV shows.
Note: the acronym TAGS refers to "The Andy Griffith Show"
http://www.retroweb.com/40acres.html
and this site explores Star Trek in particular:
http://www.mayberry.com/tagsrwc/wbmutbb/startrek/index.htm
a small example...
As Edith and Jim take in the evening air, they stroll past Floyds Barber shop and find themselves in Mayberry, North Carolina? Talk about your alternate universes!