Final answer:
The text provided does not contain enough information to answer the question about who Jethro claims is as wiggly as a groundhog in a grass fire, as the character Jethro and the comparison are not mentioned in the excerpt.
Step-by-step explanation:
The question appears to reference a character named Jethro, who seemingly compares someone's level of activity or nervousness to 'a groundhog in a grass fire'. However, the information given from the excerpt provided does not mention Jethro or give enough context to determine accurately who he was referring to. Without the specific text or context, providing an accurate answer to the question regarding who Jethro claims is as wiggly as a groundhog in a grass fire is not possible. It's essential to refer to the specific book or material where Jethro is a character to find the answer.