Actress Olivia Wilde was discussing an upcoming movie on stage this week when she received a mysterious envelope, passed across the stage by someone in the front row.

The contents, according to various reports, were custody letters from her ex-partner, Jason Sudeikis, with whom she has two children. Wilde quietly passed the opening of the letters, marked "personal and confidential", but the incident raised questions. How did the person who brought the letters enter the event at CinemaCon, a gathering of the star-studded film industry in Las Vegas? And why did the person choose such a public moment to hand over the documents to Wilde?

Sudeikis did not know that the letters would be given in such a way, otherwise he would not accept said a representative for Deadline.

But this is not the first time this has happened, says Ken Hastings, president of Hastings Legal Services in Temecula, California.

In 2013, for example, an audience member gave legal documents to singer Ciara while she was performing. A few years later, Tyga was organizing a party when someone approached him to sign some boxes - then handed him some letters and posed for a photo. Britney Spears was given papers while leaving a medical facility. And last year, Dr Dre apparently received his divorce papers shortly after attending his grandmother's funeral.

Whether or not what happened to Wilde was inappropriate, in Hastings's view, depends on whether paper service on stage was the last resort - for example, if she was "avoiding service".