Yep. One of the arguments no sane person should countenance is that Katy Perry's songwriters happened to use a four note descending synth arpeggio in an intentional attempt to cash in on the fact a four note descending arpeggio in a different key was a motif used on one of the sixteen tracks of an album which hit number five in the Gospel Charts four years earlier. For similar reasons, Universal isn't going after most of the 3.8m websites using the phrase 'phone home', and you're probably OK using three stripes in artwork unless you're drawing them on the shoulders of sportswear or sides of shoes to make it look like Adidas.

[there actually are musicians that specialise in recording backing tracks intended to resemble a particular popular recording which aren't that recording for use in commercial products, but they tend not to get sued...]

Copyright law considers the importance of a sample to the work as a whole, in addition to just the size. Any arbitrary three-word phrase from the middle of a script is probably not copyright infringement. The most memorable line from the entire movie probably is.

Related: The Supreme Court ruled that excerpting a single paragraph from a 454-page book can be copyright infringement. The book was Gerald Ford's memoirs, the one paragraph was his reasoning for pardoning Nixon. The Court's reasoning was more-or-less that nobody cared about anything else Ford did, so excerpting the one paragraph was as good as giving the whole book away for free.

The amount and substantiality of the copied portion to the work as a whole is one of the factors for fair use, an affirmative defense.

Whether a work in question is even eligible for protection at all is a distinct legal question.

Yes, but no one is disputing the legal eligibility of movies or songs for copyright protection.

The question in play is how much of of the copyrighted work may be reproduced before it is infringement.

Yes, that is very similar to the copyright argument made by Flame.

Of course not every set of four notes or eleven letters in a copyrighted work is prohibited; the significance and context of the use matters.

Wouldn’t that be considered something more like an implicitly-created trademark? It’s essentially the equivalent of a company motto for the the movie’s SPV company.