If your significant other showed up at the front door of your shared residence with a tandem bicycle and a big smile on her/his face, how would you react?

Let's go  (Champ)  ;)

Same I think that would be fun :-)

 Well, I like to ride bicycles, but we took a canoe down the river and didn't make it  too far before she lost her balance and dumped us. A tandem bicycle could be fatal! 

I would say "What do you think you are doing? You could have bought a used car for what that thing cost."

I'd be delighted! And I'd claim the handlebars so I wouldn't have to breathe farts the whole ride! :D