Who you gonna call with your 'cell' phone?

After being arrested at a protest over Sudan's crisis, George Clooney phoned his mom from the cell (Getty Images)

So, George Clooney is thrown into a cell after his arrest at a protest over the humanitarian crisis in Sudan. "You've got one call, kid," the officer says (probably). "Make it a good one." Who does he phone? Mummy, of course.

It turns out that the single phone call isn't just a Hollywood trope. Clooney didn't reveal what he told his mom but admitted to the call after he was cuffed on Friday. "Some things never change," Clooney added.

Government guidelines in Britain also permit a phone call. The Leveson Inquiry heard this month that Damian Green MP rang Andy Coulson, former News of the World editor, after he was held over alleged Home Office leaks. Rosa Parks phoned a prominent civil-rights activist after her now infamous bus arrest in 1955. In 2010, the DJ Bounty Killer was refused bail in Jamaica after using his phone call to threaten to kill his girlfriend, whom he had been arrested for assaulting.

But we return to Hollywood for the most imaginative use of the courtesy call. In The Dark Knight, the Joker dials a mobile-phone bomb he had surgically implanted into a henchman's abdomen to help him gain access to a police station – with explosive results.