The common idiomatic expression, "all that glitters is not gold," means that some things that are "gold" — things often considered attractive or desirable — aren’t necessarily good. In contrast, things that are not as appealing may actually have great value. This idea is held in numerous cultures, but the saying itself is often attributed to Shakespeare. Well-known allusions to the bard or the meaning of his words come from Thomas Gray, J.R.R. Tolkien, and some unexpected cultural sources.

Like many of the famous Shakespeare lines, "all that glitters is not gold" is an inaccurate quote. As it appears in The Merchant of Venice, the line is "all that glisters is not gold," and it is written in a locket contained in a gold casket. The Prince of Morocco, who has been attempting to win Portia’s hand, finds and chooses it. Going for the gold casket is an obvious choice, and it represents a failure on the Prince’s part to recognize that value isn’t only found in the most expensive packages.

Thomas Gray, the 17th century poet, echoes Shakespeare's sentiments in his poem, On a Favourite Cat, Drowned in a Tub of Gold Fishes. As the title suggests, a beloved cat fails to understand that all that glitters is not gold and drowns while trying to catch fish. The poem’s final three lines are: "Not all that tempts your wand’ring eyes/And heedless hearts is lawful prize;/Nor all that glisters gold." Like the Moroccan Prince, the cat’s tendency to be captivated by "gold" — the fish — overtakes its ability to choose more wisely.

Another famous use of "all that glitters is not gold" occurs in Tolkien's The Fellowship of the Ring. When the hobbits arrive in Bree they get a note from Gandalf containing a poetic quote that begins, "All that is gold does not glitter." The poem was written by Bilbo and refers to Aragorn, who at first appears to be a dangerous and disreputable companion.

Tolkien, like Shakespeare, refers to the hidden value in things that can often be overlooked, and Aragorn’s journey through The Lord of the Rings certainly proves his value repeatedly. This theme is repeated when Frodo concludes of Aragorn: "I think a servant of the enemy would look fairer and feel fouler." The author seems to caution readers to see and judge by better measures than what is apparent to the eye.

Sometimes phrases, like all that glitters is not gold, become so imbedded in a culture that they find expression in unusual places. The SpongeBob SquarePants® episode, All that Glitters provides an interesting example. The title character’s spatula breaks and he replaces it with a new shiny one, a choice he begins to regret almost immediately. Fortunately, a few days' stay in an infirmary heals SpongeBob's original spatula, and he is very glad to get it back. Even in a cartoon world, things that are glittering and new aren’t always as good as possessions that are old and beloved.