back-to-back tandem?

last week on the silver comet trail (a rails to trails in GA)

i saw a back-to-back tandem. in passing only.
i started to turn around to check it out, but didnt.
now i wish i had.

ever seen such a beast?

i wondered:

1- is the back ALWAYS the back? will it go either way?
i would hate to always be looking out the back.

PS- i PRESUME it was a regular pedaler, and not some
kinda wierd dr sesus inchworm articulating walker.