When I write tests for code, I often include references to TV or books or other such things.
If I need a text string, I rarely do "Hello World". I used to do "Hello Kitty" but these days I usually use "Hi Bob" (from For All Mankind). I even added a test API header "X-Hi: Bob" the other day. 😁
For errors I often go with "Out of cheese error" or "Divide by cucumber error" from Discworld.