Inexplicable occurrences
Else clues• Bafflers
• Baffling problems
• Brain teasers
• Contradictory characters
• Conundrums
• Head-scratchers
• Inscrutable people
• Inscrutable types
• Knots
• Knotty problems
• Mysteries
• Obscure riddles
• Paradoxes
• Perplexing people
• Perplexing puzzles
• Posers
• Puzzlers
• Puzzling posers
• Riddles
• Sphinxes
• They're hard to figure
• They're hard to figure out
• They're puzzling
• Tough nuts to crack
• W.W. II code machines