Secret agents Mortadelo and Filemón are called again by the TIA to execute a difficult mission. The criminal gang of the Rata, led by the evil Professor Apolonio, has stolen a batch of plans of a high-tech defense project from the Center of Agrounautical Research of the Cosmos, which will derail the project's development and endanger the entire country if not recovered. The two agents intercept the gang in route to leaving the country by cruiser, but in the process they discover the plans are guarded in a perilous recipient - the horn of a huge Spanish fighting bull.
It was penned by Ibáñez in a midst of heavy negotiations with its publisher, the infamous Editorial Bruguera, and has a lot of behind-the-scenes stories. The comic book was originally unrelated to Mortadelo y Filemón, instead being the first installment of what was essentially a Captain Ersatz series meant to be sold to another publisher, but when the troubles were solved, Ibáñez re-adapted it into M&F. The planned dopplegangers, Lentejo and Fideíno, can still be seen in the original manuscript of the first seven pages when looked at from the back, surviving behind the stickers used to cover them up with Mortadelo and Filemón.
This comic provides examples of:
- All for Nothing: At the end of the book, it's revealed that the secret plans never left the Center, as Bacterio accidentally switched their case with a rheumatism tab tube. To say that Mortadelo and Filemón are naturally not amused would be an understatement.
- Ambiguous Situation: It's never revealed what Project Bartolo exactly is. The context and its references imply it is some kind of defense system related to space, possibly a surveillance satellite or a Kill Sat.
- Artistic License – Geography: Played for laughs. The cruiser ship is named Ile du Soria ("Soria Island" in French). Soria is a Spanish city in midst of the peninsula, not an island.
- Badass Bystander:
- The crowd at the bullring. When Mortadelo, Filemón and the picador's horse get thrown to the rows, the people around get indignant, lift them over the head with shocking strength, and throw them back to the ruedo. Later, they also riot and jump in to beat them up when it is made clear the bullfight show is over.
- A single Bananian cop arrests Apolonio and the entire Rata gang after knocking them out in one swing of his truncheon.
- Bald of Evil: Apolonio and a couple of his henchmen have it.
- Banana Republic: The aptly named Republic of Banania is implied to be one, from its name, its location at the other side of the sea and the fact that it has bullfighting like Spain, although it is pretty indistinguishable from Spain in looks.
- Be Careful What You Wish For: A Bananian homeless asks St. John Chrysostom to send him some meat to eat. Right after, due to a series of unrelated events, the bull directly falls on top of him.
- Brick Joke: When Mortadelo gets his hand in the box he knows contains the plans, he grabs something and claims he's found the receptacle - which is actually the bull's left horn. At the end of the story, they find out that said horn was actually a fake that contained the plans.
- Brown Note: Mortadelo knocks out the bull by showing him the hotel's price list.
- The Brute: Rata's gangster Tapia, who is a big man with a bit of Super-Strength.
- Brutish Bulls: The whole story's schtick. A lot of hilarity comes out from the fact that both heroes and villains have to steer around an enormous, aggressive toro de lidia.
- Butt-Monkey: The short waiter ends up being startled by all of Mortadelo's disguises through the story, making him believe he's crazy and seeing things.
- Collateral Damage: Constant, due to the bull.
- Crouching Moron, Hidden Badass: While not as much as the previous story, mainly because the bull is so powerful and unmanageable, Mortadelo still manages to save the day and outwit the villains at a handful of points.
- Dissonant Serenity: Mortadelo clocks a Horny Vikings-dressed opera singer over the head believing he was the bull, so Filemón berates him into making sure the next time. Only that the next time Mortadelo faces the bull, he nonchalantly asks the animal if he's the Living MacGuffin they are seeking - while Filemón runs away. Obviously, Mortadelo ends up immediately thrashed around.
- Double Take: Filemón does one when a crocodile opens Mortadelo's door, first thinking he simply missed the right door and then panicking and running away. Later the bullring doorman has a similar experience.
- Early-Installment Weirdness:
- Like the previous comic book, although with some help from serendipity rather than sheer competence, here Mortadelo and Filemón show themselves as decently skilled agents and actually fulfill their mission.
- Filemón wears his red jacket, a call-back to the single-page adventures era that only appears in two full-length books (with El Sulfato Atómico being the other one) and lacks his trademark bow-tie, a side-effect of the fact that he was supposed to be a different character in the first place and Ibáñez didn't bother to redraw his entire outfit just to add that one detail when the rest was close enough already.
- Epic Fail: The title agents try to use a large party rocket to reach a truck where the bull is held, but they fail, crash and are run over. Later, their attempts to pass as bullfighters are a prolonged series of failures.
- Femme Fatale Spy: Mortadelo momentarily dresses up as one to make a joke.
- He Went That Way: After sneaking into the bullring in a bad bull disguise, Mortadelo and Filemón are being chased by the doorman. What does Mortadelo do? Quickly put on another disguise and fool the doorman into walking right up a wall.
- Hoist by His Own Petard: While Mortadelo and Filemón are being ganged up by the bullring crowd, Apolonio throws a powerful smokescreen to help Rata and company grab the bull and escape. This only results in their defeat: the smoke allows the agents escape and find the bull first, while Rata accidentally takes a cop's truncheon believing it to be the bull's fake horn, which gets them arrested.
- Killer Gorilla: Mortadelo disguises himself as an angry-looking gorilla, scaring the heck out of both Filemón and the waiter.
- Literal-Minded:
- In another mainstay of the series, Mortadelo demonstrates this in several occasions. In the first but far from last instance, he's told by Filemón to disguise himself so nobody recognize him, and Mortadelo interprets this as any disguise being valid, leading him to turn into a Killer Gorilla in midst of the cruiser's aisle.
- This time Mortadelo is not the only one, as Rata's henchmen (and Rata himself) are prone to misunderstand Apolonio's orders this way.
- Living MacGuffin: A subversion where the McGuffin itself is not the bull, but it is contained in him.
- Mad Scientist: Subverted. It's implied Prof. Apolonio is one of those, if anything because he is a professor and has kind of the look, but he's not seen doing anything related to science on-page.
- Meaningful Name: The Brute is almost completely deaf, and is called Tapia ("wall"), after the Spanish idiom "estar sordo como una tapia" ("being deaf like a wall").
- No More for Me: Although the agents disguise the drugged bull with scarecrow clothes to enter a hotel, the receptionist sees the animal's tail in their way out. He is then seen emptying a tequila bottle on a flower pot.
- Omnidisciplinary Scientist: Dr. Bacterio, who was a biologist in the previous story, is now also the chairman of something that sounds like a space agency.
- Puff of Logic: When the bullring's doorman is running up a wall thinking he's still chasing Mortadelo (see He Went That Way), he falls off as soon as he notices he is somehow running up a wall.
- Real Vehicle Reveal: Typical of Ibáñez, the story opens with Filemón being seen behind a luxury car's window... only for the car to drive away, revealing Filemón was actually riding a bicycle next to the car.
- Refuge in Audacity:
- Used constantly by both heroes and villains, counting the very usage of a bull to hide the plans.
- Mortadelo's disguises allow this very well. For example, when Mortadelo starts screaming after getting a cigar in his eye while eavesdropping on Rata's gang, Rata goes out to investigate - and finds a grazing percheron. Rata returns and calmly states it's just a horse.
- Screw Politeness, I'm a Senior!: An old lady can be seen climbing on top of people while fleeing from the bull, all while claiming to be a weak old woman.
- The Scrooge: Filemón reveals he bought tickets for the cruisers... only that, in order not to spend too much money, their cabin is the ship's chimney.
- Shout-Out:
- Like the previous comic, the story is a Whole-Plot Reference to a couple chapters of André Franquin's Spirou & Fantasio, also including many references and entire vignettes taken from other works by Franquin (not limited to Spirou but including Gaston Lagaffe). The character of Apolonio is an Expy of both Dr. Kilikil and Zorglub.
- There are several images inspired by Maurice Tillieux's Gil Jourdan: Dragonfly Escapes.
- The car's gag is taken from the 1932 film Cinemania.
- Sinister Schnoz: Evil professor Apolonio has a hooked nose.
- Tempting Fate: At the end of the comic, the waiter can be seen meditating under a tree, expecting not to find any more bulls nearby, yet just in the way of a herd of bulls Mortadelo and Filemón are directing towards Bacterio.
- This Page Will Self-Destruct: The mission's briefing is given in a large gramophone hidden in a phone box, which self-destroys after it reads its message.
- A Tragedy of Impulsiveness: Played for Laughs. Apolonio and Tapia are told by a photographer that the bull was about to exit the hotel, so they immediately jump in to knock it out with their nightsticks... only for the "bull" to be actually a hulking wrestling champion with said nickname, who promptly beats them down.
