I went out into my driveway one morning and saw the following:
What (probably quite amusing) scene was I too late to witness firsthand?
(I'm not sure how decipherable this picture is, but go on and give me your best guess! I'll mention any fun conjectures tomorrow alongside the real explanation.)
(Major impress-Dr.-Shapiro points if you can identify the kind of tree from this poor-quality photo.)
For starters, this is a grafted tree, meaning a branch of one species has been fused onto the trunk ("rootstock") of another. Remarkably, this can be done without any advanced technology—in fact, it's a routine way of growing many kinds of fruit trees. It's as if you could duct tape my arm to The Rock and end up with a buff actor with great handwriting.
In this case, a flowering cherry (the branch with the frilly pink blooms) has been grafted onto a hardier species, probably a regular cherry tree. The intention was to make a flowering cherry with the body of The Rock, so to speak.
But here's the thing about grafts: if you don't prune them, the rootstock will take over. The regular cherry tree is naturally more vigorous than the flowering cherry; that's the reason for grafting onto it in the first place. This tree seems to have been left to its natural fate.
It's possible that the owner wanted both frilly blossoms and edible cherries. You can find trees at nurseries that promise "3 kinds of fruit on the same tree!" (My neighbor has a lemon tree that produces two distinctly different kinds of lemons.) However, such trees still need careful managing or else the weaker grafts will usually get starved out.
I got a bunch of answers to this puzzle of varying specificity. Huzzah to Hazel for the most complete and precise solution!