DeGeneres, 60, explained on an episode of her talk show, originally airing Friday in the USA, that she wanted to give back to her fans as part of her 60th birthday celebration.
Unaware of what was going on, Ellen welcomed her wife to the stage of her birthday show - and it got a bit teary from there.
She highlighted some of the good deeds that the audience members did including a couple that drove 800 miles to deliver supplies to victims of Hurricane Harvey with their own money.
Her wife, Portia de Rossi, swung by to surprise DeGeneres with a birthday present.
If you didn't already know, Dian is one of Ellen's idols, and grew up following the great work she did in Africa. Inside each of those boxes of Cheerios was something that the audience would split. When every person in the 400 capacity studio lifted up a box, Ellen revealed they would be getting an equal share of a whopping $1 million. So check and see if you have a box of Cheerios under your seat.
In addition, the talk-show host managed to squeeze in a birthday shoutout to Justin Timberlake and Kerry Washington, who have the same birthday as de Rossi. DeGeneres said as her audience experienced a mix of emotions, some screaming or crying, while others stood in shock.
'Now, you will join Dian as a protector and champion of these mountain gorillas'.
While Ellen was playing a game of "Show Did/Show Didn't", in which she was challenged to recall previous interactions with celebrity guests as fact or fiction, the ABC late-night host surprised her by turning a "Show Didn't" into a "Show Did" on the spot. Ellen has been a longtime admirer of visionary scientist Dian Fossey who spent most of her life studying the rare mountain gorilla in Rwanda, ensuring their survival in the wilderness. The comedian just shared a rare PDA picture of herself and her wife, Portia de Rossi, kissing to celebrate de Rossi's 45th birthday on Wednesday.
All season long, I partnered with Cheerios to encourage people to do one million acts of good and if you're here in my audience, you helped us reach that goal.