Matthew Lawrence opened up to PEOPLE about why he dedicated his 'Masked Singer' performance of "Hallelujah" to his 'Mrs. Doubtfire' costar Robin Williams.

"Not only was he the most brilliant artist, but he was just the most compassionate, humble, good human being I've yet to work with," Lawrence told Page Six.

"I didn't quite realize it at the time, but that moment there on set of Mrs. Doubtfire, that those six to eight months were the biggest learning curve anyone can get when it comes