I recently embarked on a photo walk with a medium format camera (a friend's Mamiya RZ67 Pro II) loaded with 135 format film (Kodak Portra 400), an unconventional combination that brought about fascinating results.
One might wonder why I chose to load a medium format camera with 135 format film, typically designed for smaller 35mm cameras. The answer lies in the element of surprise and unpredictability it brings, but mostly just "Why not?". The larger film area of the medium format camera captures an extended image, exposing the sprocket holes and pushing the boundaries of traditional composition. This unexpected fusion can yield intriguing and artistic results, and create wide shots that can look quite cinematic, almost a poor man's version of a Hasselblad XPan.
Although it was quite fun to be able to shoot wide format on 135 film, ultimately lugging the Mamiya RZ67 around as a street photography camera was too much, as the camera is mainly designed for studio work. Still I loved the results that came back from the lab.