Being the center of a story, Mac Guffins tend to stack up a large number of tropes & sub-troupes.
This one Needs More Examples and Needs a Better Title. I'm still involved but this is also Up for Grabs if you want to put the work in. I realized this might be a good addition while doing some editing about The Maltese Falcon, which has about five of the MacGuffin sub-tropes all stacked on at the same time. I started thinking & realized that, since they're in the middle of things & the writer/author has to keep the plot interesting a writer will sometimes start stacking tropes up. This may qualify as a "metatrope" or some such, being a trope dependent upon other tropes. Some other examples are the Philosopher's Stone in Fullmetal Alchemist (which can be classified as about a half-dozen different subtropes of MacGuffin), "what's in the case" in the thriller Ronin (starring Robert De Niro), or the titular object in the children's novel Interstellar Pig (where the MacGuffin turns out to be a sentient being that literally intentionally changes trope every time someone gets the thing).
Hello, Unknown Troper. You'll need to get known to lend a hand here.