Phrases from television and film routinely outlast the work that produced them, remaining in general use long after the show itself is forgotten. The phrase survives by becoming useful independently of its origin.
The phrase has to do a job language was missing
Expressions that persist usually fill a gap, providing a compact way to say something that otherwise takes a sentence and a specific tone to convey.
Once a phrase does that work, people reach for it because it is efficient rather than because they are referencing anything, and the reference becomes incidental.
Phrases that carry no function beyond quotation fade quickly, since using them signals only that the speaker watched something, which stops being interesting almost immediately.
Detachment from the character is the decisive step
While a phrase still evokes the performer who said it, using it is an act of imitation, and imitation ages badly as the source recedes from view.
The phrases that last lose that association, reaching people who use them fluently without knowing where they came from or that they came from anywhere.
Delivery is what makes a line portable
Lines that spread tend to have a distinctive rhythm or an unusual stress pattern that survives being repeated by someone with a completely different voice.
That portability matters because the phrase must work when spoken flatly in ordinary conversation, not only when performed with the original timing.
Writers cannot reliably engineer this, which is why the lines that enter general use are rarely the ones a production expected to be quoted.
Repetition inside the work builds the foothold
A phrase repeated across many episodes is heard often enough to become familiar, and familiarity is what allows it to be used without explanation.
Long-running series therefore produce more surviving phrases than films, simply because a line delivered weekly for years reaches a level of exposure a single film cannot match.
The origin becomes a piece of trivia
Eventually the phrase is fully absorbed and its source is recoverable only by looking it up, which is the same path taken by expressions from older media.
Rediscovery is common, where someone encounters the original and recognises a phrase they have used for years without connecting it to anything.
That moment is a reasonable test of whether a catchphrase has genuinely survived, since it only occurs once the phrase has stopped depending on the work entirely.