When an actor tearfully accepts an Oscar, they don't actually own the golden statuette. To take it home, they must sign a contract offering to sell it back to the Academy for exactly $1.
Since 1950, this ironclad legal agreement has dictated that neither winners nor their heirs can sell or dispose of the trophy on the open market. The Academy enforces the rule aggressively through lawsuits. If a winner refuses to sign the waiver, they still retain the title of Academy Award winner, but the Academy keeps the physical trophy.
The statuettes handed out on stage are also completely blank. Because the final results are kept strictly secret until the envelope is opened, no names are attached to the awards during the broadcast. Every nominee has a nameplate pre-engraved before the ceremony, but winners must attend the Governors Ball afterward to have their specific plate screwed onto the base of their new trophy.
The physical design of the Oscar is now fiercely protected by copyright and trademark law and cannot be altered, but the Academy used to regularly bend its own rules. In 1939, Shirley Temple presented Walt Disney with a customized honorary Oscar for Snow White and the Seven Dwarfs featuring one standard statuette standing next to seven miniature ones on a stepped wooden base. The Academy also awarded a custom wooden Oscar with a movable mouth to ventriloquist Edgar Bergen in 1938.
The material itself has occasionally changed due to external forces. For three years during World War II, the Academy faced severe metal shortages and was forced to manufacture the statuettes out of painted plaster. Once the war ended, the winners were invited back to trade their plaster trophies for standard gold-plated metal replacements.