Final answer:
In the original Cranium board game, the yellow cards belong to the Word Worm category.
Step-by-step explanation:
In the original Cranium board game, the yellow cards belong to the category of Word Worm. These cards test players' knowledge of spelling, vocabulary, and wordplay. Players may be asked to spell words, unscramble letters to form a word, or guess the definition of a word, among other challenges.