It would be difficult to run into trouble by just making a cultural reference in a script. But asking lawyers if there's "any possible" legal actions will generally evoke something - we lawyers are more creative than we usually get credit for. So let's see . . conceivably, you could use a TV show or film title in a way that makes false statements and disparages the show/film and commits "trade libel," which is defamation of a business and actionable as a tort in CA.
You're best off hiring an entertainment lawyer to "vet" your script, since if you do sell it, you'll have to warrant that it doesn't infringe on any contractual, privacy, publicity, or IP rights of anyone.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
Q: Will just saying the titles or names of these characters justify any possible legal actions?
R: The mere, and sporadic, mention of a fictional character's "title" and/or name in another work of authorship raises no intellectual property issues. Depending on what is said, or can be reasonably inferred, about the fictional character, the actor portraying the character may have a claim. As noted by Attorney Koslyn, you should have your script reviewed by an intellectual property attorney before it's published or performed.
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