Starring a young Dean Jones as O'Toole, before he replaced Fred MacMurray as Disney's favorite leading man, the shipboard adventures generally involved schemes, concocted by rich but befuddled Lt. Rex St. John (Jack Mullaney) or conniving but likable Seaman Gabby Di Julio (Harvey Lembeck), that would inevitably fall apart, and require O'Toole's quick thinking to prevent discovery and retribution by Lt. Cmdr. Virgil Stoner (Jack Albertson, long before "Chico and the Man"). While the basic formula was predictable, veteran producer Jack Sonntag was not unwilling to experiment, occasionally offering a musical-themed episode, or a storyline geared to a guest star.
A favorite episode featured guest Stubby Kaye as an obese sailor facing discharge unless he shed his excess weight. Despite O'Toole's diet and exercise regimen, the sailor seemed to be gaining weight, not losing it (he had stashed goodies all over the ship). Finally, O'Toole, realizing he couldn't 'force' Kaye to lose weight, gave him an "It's up to you" speech, which hit home. Kaye started dieting and exercising in earnest, and passed his physical, then transferred to submarine service. "If I gain weight there," he quipped, "we'll submerge!"
Lacking the "Country Boy vs. Tough D.I." comic opportunities of "Gomer Pyle", or the 'Bilko'-like shenanigans of "McHale's Navy", "Ensign O'Toole" was, perhaps, too sweet-natured to become a hit series, but it could bring a smile, and was as affable as it's good-natured star.