In his column for Event magazine, Piers revealed he bumped into the actor at the Help Haiti Home gala in Beverly Hills earlier this month where the new couple made their first public appearance together.
Charlize Theron and Sean Penn
"At 2am, Sean came over, and bear-hugged me," he wrote. "'Congrats on a great night,' I said. 'And congrats on Charlize too.' He laughed. 'She's a keeper, that's for sure... well, I'll do my best to keep her anyway!' "
And Charlize paid back the compliment, describing the 'Milk' star as a "great guy".
Piers wrote:" 'I'm so glad you two have got together,' I said, 'Sean's a great guy.' 'I know,' she smiled, putting her hand round his shoulder."
*rushes out to buy hat*