「あんたもマンガだ！！」 - how to understand it?

Question

Here is a page from a classic manga ドクタースランプ: http://i.imgur.com/9UGI9kI.png In this chapter the professor shows Arale a camera than can look into the future.

In the bottom frame Arale says to him that this reminds her of ドラエモン, to which he replies 「あれはマンガ！」, and then the narrator says 「あんたもマンガだ！！」. What does the last phrase mean exactly? Is it a shortening of "you're in a manga too!", or does マンガ here mean "a manga character" (again in a shortened version perhaps?), or what? Is it just like how in English you can call a cartoon character a cartoon? (at least I think you can)

Answer 1

「あんたもマンガだ！！」

is not a shortening of another phrase per se. That would only be a "fast and convenient" explanation that people (myself included, I admit) tend to use with Japanese-learners in answering questions like this. This is just how we speak and we are not omitting any words either intentionally or unintentionally.

Saying that is a shortening of something like 「あんたもマンガのキャラだ！！」 might appeal and satisfy many, but it simply is not.

Here, 「マンガ」 refers to "everything pertaining to manga" and that would naturally include manga characters. What matters in this context is whether something/someone belongs in the manga world or the real world.

Translation, however, is another matter altogether. If the sentence "You're manga, too!" made sense, take it. If it sounded better to say "You're a manga character, too!!", take that instead.

Finally, the advanced learners should know that this type of statement used in fiction is called 「メタ[発言]{はつげん}」. That is when a character talks to the readers and such. In this case, the narrator is talking to a character. In theory, this should not be possible, but it is practiced in some fiction.

Answer 2

「あんた」 is a shortening of ”あなた" (you) and マンガ is an exaggerated way to write 漫画, which refers to comic books as you know.

So in this case, Arale is saying that "Doraemon" is only a comic book who isn't real, to which the narrator is saying to Norimaki Senbei that he is part of a comic too. The line doesn't literally mean "manga character", but it amounts to the same idea.

I haven't read Dr. Slump too much but from what I have seen, it is pretty self-referential and jokes like this are somewhat common.