Heard this from someone on the inside: You can get literally anything classified.
Something that they used to do for the fun of it was write these totally outrageous bullshit papers, you like like just making up random conspiracy theories... Type it up as some addendum report to some (classified) project you're working on, boom, it's classified.
It's not an actual project deliverable so no one reads it.
So then, he'd send the report to the GAO or IDK what, whatever organization is in charge of *declassifying* stuff. Reviewer would look at it and be like "lol wut ... whatever, has nothing to do with anything that actually matters" and approve it.
Now they go run around with a DECLASSIFIED document that says the earth is hollow and there's a worm civilization, or whatever...