It is not uncommon to see a screenplay refer to a real person or use a real person as a character, but we recommend you tread lightly, as it could be considered libel.

In general, it’s okay to refer to a person in his or her known capacity, ie, “…like when Mark Zuckerberg created Facebook!” However having Mark Zuckerberg as a character opens many new legal challenges.

The best advice: when in doubt, consult an attorney.