Frank Sidebottom was a peculiar stage character defined by his enormous papier-mache mask, immortalized in countless UK TV appearances and a fictionalized biopic produced after the 2010 death of creator-performer Chris Sievey (previously at Boing Boing). Sievey included fascinating codes with Frank's promotional material, and British intelligence officers finally cracked it. It was hard to crack because half the characters were nulls.
"By letting his kids add nonsense into the message, it deliberately obscures the chances of anybody – even top mathematicians – being able to crack it. So I reported back to GCHQ that the outer ring is a red herring and then had an email one day saying, 'Right, we've cracked it during a light-hearted training exercise.'
"I'm embarrassed to say, on the very next day Chris's very own code grid was found in the back of his address book. It was almost like Chris Sievey was going, 'There you go, now we've all had our fun, there's the explanation.'"