I quite often use movie, and other pop culture, references. For example, in development and test mode pages include a Pi symbol in the lower left corner which shows some debug information when you click on it.
There have been cases where the final error message was PC Load Letter, if no better error message was available.
PC Load Letter
Or when resizing an array the comment // We're going to need a bigger boat is very suitable.
// We're going to need a bigger boat
For an internal CA I used the department name Setec Astronomy.
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