A series of children's puzzle books by Martin Handford, featuring the character Waldo (Wally in the UK) who must be found hidden in detailed illustrations.
↗ View on AmazonMentioned once in Halloween.
Halloween
Season 5 · Episode 3 · S05E03
“Waldo! From 'Where's Waldo?' He's like in sixteen books!”
From the same episode and category.
“Tonight, you'll be Lord Peter Wimsey! ... He's a celebrated bon vivant sleuth from a series of novels by Dorothy L.…”
“He's a celebrated bon vivant sleuth from a series of novels by Dorothy L. Sayers.”
“I thought you said you were getting me a Sherlock Holmes outfit.”
“I'm going to go as Cyrano de Bergerac—musician, philosopher, fighter, poet!”