Actually, there is a big difference. In the example you cited, the character knew that what she was saying was a pop culture reference. Heck, you even had the character state right afterward what was being referenced, for good measure. In what the plagiarist did, the characters were not making pop culture references, the author was. Without stating what was being referenced.
Consider this scene from The Gift:
SPIKE: Well, not exactly the St. Crispin's Day speech, was it? GILES: We few...we happy few. SPIKE: We band of buggered.
Shakespeare's not exactly Pinky and the Brain, but still. I'm sure that a lot of the audience did not know what the heck Spike and Giles were talking about. But even without getting the reference, it's pretty clear from the context that these characters were quoting something else. It gets trickier if the characters aren't aware of the reference, but it's not impossible. As long as there is no way that people might think you came up with the words or ideas in question yourself, like your recent "plane on snake" fic, that's fine.
no subject
Consider this scene from The Gift:
SPIKE: Well, not exactly the St. Crispin's Day speech, was it?
GILES: We few...we happy few.
SPIKE: We band of buggered.
Shakespeare's not exactly Pinky and the Brain, but still. I'm sure that a lot of the audience did not know what the heck Spike and Giles were talking about. But even without getting the reference, it's pretty clear from the context that these characters were quoting something else. It gets trickier if the characters aren't aware of the reference, but it's not impossible. As long as there is no way that people might think you came up with the words or ideas in question yourself, like your recent "plane on snake" fic, that's fine.