The Turtles journey through the cosmic ocean of Varuna, where they must prove themselves worthy to Hiidalra. Hiidalra is an aquatic alien queen who holds the second piece of the black hole generator.
- Admiring the Abomination: Casey, as usual provides some of this, declaring Armaggon his "favorite bad guy ever."
- The Chains of Commanding: Leo is painfully aware that as leader of the team, the fate of Earth rests most heavily on his shoulders and the decisions he'll make from here on out.
- Combat Tentacles: Cthugha and Hiidrala both have them.
- Fish People: The Daagon greatly resemble Deep Ones.
- Mythology Gag: Electric Seaweed has also shown up in the first NES Video Game
- While speculating on what Cthugha will look like, Mikey imagines that he'll most likely look like Ray Fillet.
- Proud Warrior Race: The Daagon.
- Replacement Goldfish: Leo confides with a holographic simulation of Splinter for wisdom in place of the real Splinter, which the other guys think is unhealthy.
- Running Gag: Raph gets nauseous in space. Yet again.
- Scenery Porn
- Shout-Out: David Tennant (a Doctor Who alumn) quoting Star Trek gives a lot of people Nerdgasms.
- The Daagon home city looks a lot like Otoh Gunga.
- The Daagon and Cthugha in particular are shout outs to H. P. Lovecraft's Cthulhu Mythos (although the Cthugha is In Name Only).
- Skeletons in the Coat Closet: The Daagon wear skulls as arm-guards.
- Space Is an Ocean: Literally.
- Summon Bigger Fish: Cthugha, nuff said
- Taking the Bullet: Leo takes a missile blast for Hiidrala, not only saving her but proving him self worthy to take the black hole generator.
- Too Spicy for Yog-Sothoth: The Cthugha spits up Armaggon and Lord Dregg and retreats after his Vreen minions come rescue him.
- Unscaled Merfolk: In contrast to the rest of the Daagon, Hiidrala resembles an octopodian mermaid.
- Unusual Euphemism: Fugitoid, parodying the Sound-Effect Bleep."Oooh, Bleep!"
