On Drew's advice, the family goes to a vacation resort and health spa, where Stu can work out, relax, and become "a whole new man". Tommy, however, is worried that the workout would make Stu mean. - Description from Klasky Csupo.
Stu gets worn out taking care of Tommy and Dil so the adults send him on a spa treatment to make him feel better.
The storybook adaptation of this episode, Brand-New Daddy, notably adds Kimi to the story, despite the fact that she isn't in the actual episode (as it was produced and aired about two years before her debut in Rugrats in Paris: The Movie).