Astro-Gnar
So we have Astronaut Teemo and Astro-Nautilus , but why not Astro-Gnar? I mean it even has the same play on words thing as Astro-Nautilus...
Mini:
Q: Space Boomerang (based off of Astro-Nautilus's anchor)
W: You know the targeting reticle (in spaceships) from Star Wars? That kinda thing.
E: When he jumps he's propelled by a small burst of air (like the fire-extinguisher thing from Wall-E)
R: 
Mega: Q: Either a space-rock or a lunar lander. W: Not really sure... E: Same thing as Mini-Gnar R: Not sure for this one either
Enjoy, and feel free to give me advice!
