The best piece of advice I can give for a Homemade Banana Couple Halloween Costume Idea like this is… Thrift Stores! They generally carry the widest range of color and style options for costume clothing, and are always the cheapest.
My friend Evan and I wanted to dress up as bananas, but were not satisfied with the pre-made banana costumes available online or in stores. So, we each assembled outfits of all bright yellow clothing. I think my jacket was made a womens Liz Claiborne blazer, but it worked just fine for my purposes. It doesn’t matter the make, as long as the color matches and it is in good condition. A pair of yellow dress pants and an inside-out t-shirt were also picked up. A set of long underwear worn underneath provided useful for going out on a cold night in the northwest.
Yellow spray paint helped accent our sneakers and sunglasses, and we each constructed our own heads. We used coat hangers and yellow nylon, similar to a kite material, chosen for its light weight, breath-ability, and bright color. I always enjoy trying out a costume, rebuilding it, and trying it out again many times. I have gotten a lot of mileage out of this banana head, and have rebuilt it a number of times, and this wire frame design has been the most sturdy and efficient that I have made up. When framing around your head, be sure to build it large enough to not squeeze your head or face, but not too large that it loses its stability resting on the crown of your head.
Attach wires together by coiling one end around another – all touch points from wire to wire are coil wrapped to that head does not rock back and forth when worn. I cut up a few socks and taped them into the inside of the frame so the parts resting on my forehead and crown would be more comfortable over a long period of time. The nylon, cut to shape, was wrapped around the frame, tucked in, and taped with yellow duct tape. I also cut the bottom edges of the headpiece in a zig zag pattern and hemmed the edges with the duct tape.
This was a fun costume to make, and has gotten me many compliments!!