Space Heroes is Leonardo's favorite show and he idolizes the main character, Captain Ryan, as a great hero. Captain Ryan is in charge of the crew of the Dauntless; the name of the ship having been identified by name in New Girl in Town.
Leonardo is first shown watching Space Heroes in Rise of the Turtles, Part 1. He memorizes one of Captain Ryan's speeches and quotes it verbatim later in the episode. He also imitates Ryan by slapping Michelangelo in an attempt to calm him down.
Leo watches the show again in I Think His Name is Baxter Stockman, Metalhead, Panic in the Sewers, Mousers Attack! and It Came From The Depths. Each time, Space Heroes seems to foreshadow something that will happen later in the episode. For example, in Metalhead, an alien takes control of Dr. Mindstrong by attaching itself to his head. The same thing happens later when a Kraang takes control of Donnie's robot, Metalhead.
There is also a Space Heroes pinball machine in the lair, which Raphael can be seen playing in the opening. Donatello uses the back of a Space Heroes movie poster for his "Hang with April" flowchart in Monkey Brains. The poster is a reference to Star Trek III: The Search for Spock (Space Heroes III: The Resurrection of Mindstrong). Leonardo also owns a vintage Space Heroes comic book, which is modeled after the first Star Trek comic from 1967.
In Season 1 of the series Leonardo watches 10 episodes of the show.
The show later gained a sequel in Space Heroes: The Next Generation.
- Captain Ryan (voiced by Brian Bloom) - The leader and main protagonist.
- Crankshaw (voiced by Scott Menville) - A young ensign who Ryan slaps every time he starts panicking.
- Dr. Mindstrong (voiced by Ben Cross) - An alien scientist.
- Commander Grundch (voiced by Nolan North) - The second in command.
- Rodriguez (voiced by Greg Cipes) - A crew member in orange shirt from "Mousers Attack!"
- That Other Guy (voiced by Rob Paulsen) - A crew member in purple shirt from "Mousers Attack!"
- Celestial (voiced by Anna Graves) - Captain Ryan's love interest and enemy.
- Hypnotica - An evil female alien who controls Captain Ryan in Parasitica.
- Panicons - An evil giant robots that shot Captain Ryan with their Anxiety Ray in "Panic in the Sewers".
- Trumplets - A cute inconvenient furry creatures (an homage to Star Trek's Tribble Tribbles, but with organic trumpets added).
- Cortexicons - a creature that took over Dr. Mindstrong's mind in "Metalhead".
- Shahana another love interest of an older balding Captain Ryan seen at the start if When Worlds Collide Part 1.
- Scronus - in When Worlds Collide Part 1 Ryan says "port me up Scronus" resembling James Kirk's "beam me up Scotty", indicating this may be an engineer.
Episodes featuring Space Heroes
- Rise of the Turtles, Part 1 -
- I Think His Name is Baxter Stockman -
- Metalhead - The Cortexicons attempt to take over Dr. Mindstrong's mind.
- Panic in the Sewers - The Panicons shoot Captain Ryan with their Anxiety Ray.
- Mousers Attack! - Captain Ryan chooses Rodriguez and That Other Guy for a suicide land mission where they would sacrifice themselves so that Captain Ryan and Crankshaw can survive. Rodriguez and That Other Guy didn't know about their mission being a suicide mission.
- It Came From The Depths - The Trumplets have invaded Captain Ryan's ship where Captain Ryan gets hooked on their cuteness until he outgrows it and has them dumped into outer space.
- New Girl in Town - Celestial attempts to seduce Captain Ryan into giving her the secret codes only for Captain Ryan to disintegrate her. Though Captain Ryan mourns her and keeps her smoky boots as a momentum.
- Karai's Vendetta -
- Parasitica - Hypnotica takes control of Captain Ryan's mind so that he can marry her.
- Booyaka-Showdown - The Destructinators are about to destroy Dauntless, Captain Ryan sacrifices himself and the ship, allowing his crew to escape.
- The Destructinators are named after the one-off villain of the same name in the made-for-TV movie "Wishology" of The Fairly OddParents, another show by Nickelodeon.