Supernovas are also gray. That's my favorite version.
Here's an idiosyncrasy: Miras have an attachment called the Wonder Wheel. Finding a ready-made replacement tire that is the proper size is impossible and so work-arounds have to be employed, i.e. they might be gaskets or other plumbing supplies, O-rings, etc. Finding all the cams can be difficult (and expensive) although I believe there are only 4 total. And you have to have the linking arms to attach to the levers of the machine.
Here's my BU (not a Nova), just for reference:
