Grandpa Lou's character in the original "Rugrats" series was known for being a World War II veteran with a strong connection to his past, often seen as forgetful and hard of hearing, but also wise and caring. In the reboot series, Grandpa Lou has been significantly reimagined. He is now portrayed as younger, not old enough to have been a World War II veteran, and the creators have taken a different approach to his character. He is still endearing and caring but with a modern twist. For instance, in the reboot, he is shown to be more involved and active, such as participating in a dance competition, which was a stark contrast to his character in the original series. This change reflects an effort to modernize the character and make him more relatable to today's audience. As mentioned in a review on IMDb, "Betty and Grandpa Lou probably are the most changed, with her now a single mother and Grandpa now too young to have been a World War 2 veteran, but old enough to have a fresh and active take on life." This shift in character traits aims to provide a new perspective while still honoring the essence of Grandpa Lou that fans of the original series loved.