Olivia Wilde fooled everyone with her crazy ALS challenge! See what she did here!

Los Angeles - Olivia Wilde poured a bucket of breast milk over her head on Saturday.

The 30-year-old actress - who has a four-month-old son Otis with her fiancé Jason Sudeikis - put her own spin on the ALS Ice Bucket Challenge, which is normally completed with water, by dousing herself with icy milk.

In a video clip posted on YouTube by her fiancé, Olivia said to the camera: "I hope it's ok, I couldn't find any water so I'm going to use breast milk."

Olivia shared the clip on Twitter on Sunday:

http://t.co/fyJ47v3z9n Your turn, @CoryBooker, @GloriaSteinem, @3RDEYEGIRL. Donated in honor of my buddy Scott Lew. http://t.co/15VLOghdIb

— olivia wilde (@oliviawilde) August 24, 2014

The brunette beauty nominated "Cory Booker, Gloria Steinem and the artist currently known as Prince," to take part in the challenge, which aims to raise money and awareness for Lou Gehrig's disease.

After having convinced everyone that she drenched herself in breast milk, Olivia tweeted again to say that she pretty much fooled the world:

Oh wait some of you thought that was really breast milk? Oh dear. Uh thank you? But my boobs aren't that generous. Haha.

— olivia wilde (@oliviawilde) August 24, 2014

Meanwhile, the stunning star, who was photographed breastfeeding her son for Glamour magazine, recently admitted feeding Otis has become part of her identity.

She said: "Being shot with Otis is so perfect because any portrait of me right now isn't complete without my identity as a mother being a part of that. Breastfeeding is the most natural thing."

The Longest Week star added: "I don't know, now it feels like Otis should always be on my breast."