The film tells the story of Andy Petrovic, a young Yugoslavian boy who discovers that his mule Gus has the astounding ability to kick any kind of ball up to 100 yards when Andy says the Yugoslavian word "Ojigdz".
Last film appearance for Bob Crane, who plays an announcer.
Tropes found in Gus include:
- Accidental Athlete: Gus would count as a rare animal version of this trope.
- Alcohol Hic: Happens to Gus after Spinner drugs his water and oats with alcohol. This results in Gus inadvertently causing chaos and failing completely at the game.
- Animal Athlete Loophole: When Gus goes out into the field to make a field goal, Johnny Unitas reads from a booklet of sport rules that a player can be a man, a woman, or even a mule.
- As Himself: Johnny Unitas plays a commentator in this film under his own name.
- Bedsheet Ladder: Andy does this as an attempt to escape from the hospital room that Spinner trapped him in, but it's subverted, as it's actually a ploy to lure Crankcase into the room so that Andy could escape while Crankcase is distracted.
- Brand X: While set in the NFL, the California Atoms and Michigan Mammoths are the two rival teams instead of the Los Angeles Rams and Detroit Lions.
- Deadpan Snarker: Johnny Unitas (playing himself), in contrast to his commentating partner, Pepper Allen.
- Doomed Supermarket Display: Gus knocks down one of these while Spinner and Crankcase chase after him in the supermarket.
- Epic Fail: At the beginning of the film, everything goes wrong during the Atoms' training practice, ranging from a marching band tripping up while a tape recorder was revealed to be playing the music to a group of inept female cheerleaders (known as the "Atomettes") falling down every time they did their pyramid routine. There's also Andy's attempts to try to play soccer like his brother Stjepan, which results in Andy falling down the well.
- FaceHeel Turn: Rob Cargill, a former member of the Atoms, switches teams after being replaced by Andy as Debbie's boyfriend, which leads to Rob trying to take Andy and Gus out of the game.
- Horsing Around: Not actually a horse, but Gus would count as an example of this trope.
- Large Ham: Bob Crane as Pepper Allen, in contrast to his commentating partner, Johnny Unitas.
- Left the Background Music On: At first, it appears that the marching band Coach Venner hired was experienced, until the baton twirler drops his baton and trips over the dropped baton, knocking over the band members while the music is still playing, before a bass drum rolls over the tape machine that the music was playing on.
- Meaningful Name: Spinner and Crankcase get their names from two parts of an automobile, the former being a type of ornamental hubcap and the latter being a type of internal combustion engine.
- Playing Against Type: Tim Conway, best known for his protagonist roles, plays the conniving Crankcase in this film.
- Those Two Bad Guys: Spinner and Crankcase
- Villainous Breakdown: Not exactly villainous, but when the Atoms are triumphant in winning the Super Bowl, Pepper becomes so shocked about how wrong his predictions were that he is reduced to just squawking in gibberish, leading to Johnny to take over the rest of the commentary.
- "Well Done, Son!" Guy: Andy appears to be this to his father, who only regards Andy's older brother Stjepan as a true hero, due to the fact that Stjepan is a real soccer pro.