"I believe Corbett is available."
"Tom Corbett?" said Proton in disbelief. "That space cadet!"
For those of you who came here looking for the term's idiomatic meaning, that's a Cloud Cuckoo Lander.
As for actual space cadets:
A Discredited Trope from the early Pulp Magazine days of media science fiction (peaked in the 1950's in movie serials and TV shows), involving a hero who was part of an organization that handles law and order in outer space, much like in a Western... in space. Frequently the titular Space Cadet was a child or teen who was a new recruit or a sidekick to an older hero. May be the equivalent of Walking the Earth with isolated outposts and frontier planets; especially strange when the Kid Hero seems not to have a family at home. His training place would be the Space Cadet Academy.
- Commander Cody.
- Buck Rogers, especially in the comic strip and movie serial, where the kid sidekick Buddy was added.
- Dickie in The Adventures of Captain Bucky and his Space Marshals, in Outer Space.
Dickie: Gee golly, Captain — I would have never thought of that!Captain Bucky: Well Dickie, that's why you're not The Captain.
- The Last Starfighter is about an Earth teen who gets recruited by aliens for this sort of organization.
- What Jim becomes in Treasure Planet.
- Space Cadet: By Robert A. Heinlein. Notably interesting for being perhaps the Ur-Example, and showing what modern readers will easily recognize as a cell phone in the opening pages.
- His earlier story Misfit also fits the trope, and makes the inspiration from the Depression-era Civilian Conservation Corps more explicit.
- Tom Corbett, Space Cadet (based on the novel)
- Isaac Asimov's The Complete Adventures of Lucky Starr: David "Lucky" Starr is a young member of Earth's Council of Science, and is in his early twenties. Rather than being a sidekick, he has one in the form of John Bigman Jones, his unofficial buddy in their quest to keep the solar system safe for the average citizen and foil the plots from the Sirian colony.
- Isaac Asimov and Janet Asimov's Norby Chronicles: Jeff's older brother is a member of the Space Police, and Jeff buys Norby to help himself study for school, which is the pseudo-military academy required for the Space Police, making the titular character the sidekick to the Space Cadet. A sidekick who ends up being the cause of most of his (mis-)adventures.
- David Weber's Honor Harrington:
- Harrington herself in the novella "Ms. Midshipwoman Harrington".
- The Star Kingdom: Stephanie Harrington and several of her friends are Probationary Rangers with the Sphynxian Forestry Service. Sort of a Reconstruction of the trope, as Stephanie was made the first such Probationary Ranger to justify the Forestry Service keeping tabs on her to keep her out of trouble.
- The Scott Saunders Space Adventure series by Patrick Moore.
- Tom Corbett: Space Cadet: Tom, as well as his companions Astro and Roger Manning, are all cadets on a training ship.
- Space Cadet Happy from Space Patrol (US) although he was more like a Number Two. Some of the Chex commercials, however, followed this trope a little better, with kids dreaming about being on the Space Patrol.
- The Video Ranger from Captain Video and his Video Rangers
- Winky and Tagalong Kid Bobby from Rocky Jones, Space Ranger.
- Wesley Crusher represents the best example in the Star Trek universe. As a child prodigy, he represented an Audience Surrogate for a young viewer and could be considered a "sidekick" to Picard. Later in the series, Wesley became a literal cadet in Starfleet.
- The elite cadet group "Red Squad" featured in Star Trek: Deep Space Nine is something of a Deconstruction of the trope — especially in the episode "Valiant", which shows what happens when a group of cocky cadets get to fly their own ship without adult supervision. They attack a Dominion battleship and get blasted to hell.
- Nog becomes a cadet in Season 3 of DS9 before his Rank Up to Ensign.
- Star Trek: Voyager
- The Outer Limits (1995):
- In "Quality of Mercy", Bree Tristan tells Major John Skokes that she is a cadet 2nd class who was assigned to Europa base and that she was captured by the aliens while on a training mission with her instructor Commander Hartley. In the final scene, it is revealed that Tristan is in fact an alien in disguise. It is not made clear whether Tristan was a real person whose identity the alien assumed or whether she was merely a creation of the aliens.
- In the sequel "The Light Brigade", the cadet (also played by Wil Wheaton) was assigned to the Light Brigade during its mission to destroy the aliens' homeworld with a subatomic bomb due to the influence of his father, a member of the UNDF Council. He wanted to be one of the 600 heroes who would save Earth from the aliens. It doesn't go according to plan.
- Buzz Lightyear from Toy Story is an homage/parody of this trope. He later received his own spinoff Buzz Lightyear of Star Command, in which he plays the trope straight.