I believe it's called a "Buddy Cycle", not to be confused with either of the the two different two-wheeled incarnations of the "Buddy Bike".
They were only produced for a short period of time a long time ago. Do some homework and read the old reviews on the 'bent forums before deciding what it's worth to you.
FWIW: It's technically called a "sociable" cycle", which is any type of a "pedal-powered cycle" having two, three or four wheels where the riders sit side-by-side.
There is a better-quality version sociable recumbent on which the Buddy Cycle was based called the J2B:
http://www.justtwobikes.com/