Walt,
It is neither necessity nor an obsession. Bananas are FUN! Like a few others here, I enjoy the sensations of fullness AND expulsion; bananas are great on both counts! Moreover (ask Susie?), because the fruit is entirely encased in its skin, it is sterile and safe to insert if you peel and insert directly.
They are a bit tricky to get in, but once you have loosened your anus with some appropriate stretching, they slip right in like a penis in a pussy. After about two or three, my rectum is full! But if I keep on pushing them in, then something intriguing happens! The fruit is squishy and a natural lubricant, so the pressure in the rectum will open the 'flap' that separates rectum from descending colon, and the lead banana glides right up the pioneer trail. The more you push, the more you can get in. My record stands at 26, but they weren't premium size - just the ones we grow here in the garden.
With that many in me, I can feel them pushing up under my rib cage, and the outline of my distended colon snaking all the way across my belly. For me,they never go past the sigmoid flexure in my colon, so the limit is about 2 litres.
The next plus is that the sugar in the bananas is an irritant, so they begin to want out with some urgency! If you enjoy holding an enema, these are among the ultimate hard-to-hold thrills. They don't gripe, but you surely want to go! If you are going to try this, I suggest wearing a VERY old pair of underrods, because you are going to be messing them quite seriously. Bananas ooze!
For the diaper fans among us, try this. Do a good clean out first so that the descending colon is empty. Fill to the brim with bananas, don diaper. Try all you like, but you will mess the diaper; and if you did the banana fill diligently, you will not only fill your diaper but it will overflow. If you aren't a diaper fan, don't try this unless you are in the shower or the tub!
Johnny