The actor was working on the charity's yearly telethon to learn more about different charities to apply to his own foundation.
Johnson has worked tirelessly on charity Love Your Sister alongside his sister, Connie, who is suffering from terminal breast cancer.
RELATED: Samuel Johnson tells his sister Connie how much money they've raised for charity
Last month Johnson took to national TV to announce the staggering amount of money his Love Your Sister campaign had raised to date.
While appearing on Channel 9's TODAY show, the actor read out that the organisation has raised more than 2 million dollars.
Johnson surprised his sister who had not known how well the donations were going."I’ve just updated the most recent report and it’s as accurate as can be but donations are still ticking in so it’s not over.” Giddy with excitement he revealed, “Donations flooded in over night, $2, 221,000!”
Another grand effort for the actor and his sister.