Folks who grew up in Oregon may remember the days when Coffee People outposts dotted the landscape, staring down Starbucks from across the street (as far as I know, the only remaining Coffee People is in the Portland airport, and the rest were converted into Starbucks shops after the sale in 2006.) When I wasn't caffeinating at Rimsky's or The Pied Cow, I spent most of my teenage years in one Coffee People or another, almost always drinking a banana milkshake.
The banana milkshake is dangerous territory—fake banana flavor is a horrible idea, and when you want a milkshake, you don't want a smoothie. A banana milkshake must balance creaminess and frothiness, be sweet and ice cold, and clearly be made from more ice cream than fruit. Coffee People had the milkshake down, though, incorporating probably a pint of their delicious vanilla-laced banana ice cream and just a little fresh banana along with what was certainly a hefty pour of cream. Suffice it to say, these milkshakes might not have been the healthiest part of my teenage diet.
I have yet to find a worthy substitute, and perhaps there's a bit of nostalgia coloring my judgment, but I believe no one can recreate this superlative treat because there isn't a lot of good banana ice cream on the market. If you've found some, please let me know. I've got a blender handy.