Movies
You know, what this room needs is a really big oversized poster of Atlantic City...oh wait, there's one.
— Charlie • So I Married an Axe Murderer

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker proposes a huge poster, then points out that the room already has one. The delayed recognition can be read as mock praise of something hard to miss. The joke draws attention to the poster by pretending to discover it.
Context reviewed