Oh! Edo Rocket is a pretty recent anime, so I hope I haven't butchered the tags or anything, because it currently appears that there are no other images with the tag oh!_edo_rocket.

There's probably some colloquial usage of 溶け I'm unaware of, as well. Feel free to change "Meltreka" to something more appropriate.

As far as I can tell 溶けレカ is referring to Eureka in latter episodes when she has short messy hair and scars/lesions on her skin. MeltReka seems good.

Also, I'm guessing the 'Eureka' on the far left is in fact Anemone, mainly based on the unidentified animal she's holding. The Cast section doesn't agree though.

Well, the leftmost Eureka has true Coralian eyes, so it's unlikely to be Anemone. Of course, Anemone's hair color is also different, but that's easy enough to fix, unlike the aforementioned issue.

南北 said:
「溶けレカ」ってのは、エウレカセブンの物語の中盤(25話近辺)で、エウレカがコーラリアンに取り込まれてしまって溶けた姿の事を言います。ベリーショートでおでこに傷のある姿。溶けてるエウレカなので略して「溶けレカ」です。

「溶けレカ」 refers to the middle part of the plot of Eureka Seven (around episode 25), when Eureka is almost absorbed by the Coralians and starts looking melted. With very short hair and scars on her forehead, that look. So that's called 溶けてるエウレカ [melting Eureka], and abbreviated it's 「溶けレカ」.

So it looks like "Meltreka" is indeed mostly correct. :) To be honest, I forgot why Eureka looked like that in the first place, so after being reminded of that, this seems not so mysterious after all...

Edit: oops, spoilers.

Uh, Kayako, how is this related to the actual eureka 7 movie?

The Eureka in the front is how she's appeared in the movie promo art. Plus its obviously referencing the movie as well as the series.

There was promo art for the movie 14 months ago when this image was made?

Apparently, since the outfits being worn by Eureka and Renton in that image never appeared in the series.