there's a bike for sale in the paper that says 1-2 person, 3-5 wheeled bike, i'm gonna go look at it tomorrow.
apparently it's a tricycle with a detatchable trailer that can also pedal. anybody heard of one of those things? i'm thinking it might be one of those things you rent to tourists at beachtowns. anyone?

Yes, Penninger Recumbents markets two models of trikes -- the Voyager and the Traveler -- that can be "mated" together to create a five-wheel tandem (photo below). I'm sure others with trikes offer similar "piggy-back" options.

https://www.penningerrecumbents.com/index.html

The Penningers are not inexpensive; however, they are well made using top-end components and allow couples with physical disabilities or limitations the ability to ride together when either one or both could not do so on their own. There was a wonderful couple from Clermont, FL, who attended the 2003 Georgia Tandem Rally at Statesboro, GA, who had a mated pair of the Penningers (see below).