Doublets is a word game, or "form of mental torture", invented by Lewis Carroll at the request of some female friends who complained of having nothing to do. He published the rules of the game in Vanity Fair in 1879, explaining that the challenge was to link two words by creating a series of new words, changing just one letter in each step. He supplied an example, in which he showed how HEAD could be changed into TAIL by carrying out the following steps:
Carroll originally called this game 'Word-Links' but later switched to 'doublets'. The game remained popular throughout the 20th century, known by a variety of names, such as Word Chains, Word Ping Pong and Transformations. In his novel Pale Fire, Vladimir Nabokov refers to the game as Word Golf. Today the game is better known as Word Ladders.
Although Lewis Carroll invented a complicated means of scoring, the main aim is to use as few steps as possible - at most the number of steps as there are letters in the words being transformed. The best examples are those where the words are linked in some way, such as with the antonyms (opposites) HATE and LOVE, LIVE and DEAD, or (especially difficult) SMALL and LARGE.
In later publications Carroll challenged his readers to:
Drive PIG into STY
Raise FOUR to FIVE
Make WHEAT into BREAD
Can you rise to the challenge?
Perhaps you could come up with your own pairs and add them as comments.