Chris Pratt, Brian Grazer, Gwen Stefani Jump on Hollywood Bandwagon Taking Ice Bucket Challenge (Video)

Chris Pratt, Brian Grazer, Gwen Stefani Jump on Hollywood Bandwagon Taking Ice Bucket Challenge (Video)

“Guardians of the Galaxy” star and Imagine Entertainment co-founder join Oprah Winfrey, Justin Timberlake, Justin Bieber, Matt Lauer and Taylor Swift in getting soaked for the ALS cause

Chris Pratt is the latest big name to jump onto the the Ice Bucket Challenge bandwagon, and he seems to have had a darn good time doing it.

The “Guardians of the Galaxy” star gave it a shot Saturday – a couple of them, actually -and then threw down the gauntlet to his Hollywood pals. Pratt challenged his ”Everwood” co-star Gregory Smith, his ”Parks and Recreation” co-star Nick Offerman and Dave Bautista from “Guardians.” This weekend producer-director Brian Grazer, who co-founded Imagine Entertainment with Ron Howard, also went under the ice with his fiance Veronica Smiley. (Watch videos below)

The list of Hollywood and media types who've gone under is long and growing. There's Oprah Winfrey and best friend Gayle King, Justin BieberSelena 
GomezMatt Lauer, Taylor Swift and NBA star LeBron James, to name just a few. (Click on the links to see their dunks.)

In case you've been off the grid lately, the Ice Bucket Challenge is an online trend aimed at raising awareness of – and money to fight – Amyotrophic Lateral Sclerosis, more often known as ALS or Lou Gherig's Disease. The trend went viral after Pete Frates, a former Boston College baseball player with hopes of starring for the Red Sox star who had his career cut short by the disease, nominated fellow Boston athletes to take part. Justin Timberlake got things going early on.

It involves people pouring a freezing cold bucket of water over their heads to raise money for charity before nominating other people to get involved. You can get soaked, or make a donation, but a lot of people are doing both.

Also watch: Mickey Rourke Gets Soaked in ALS Ice Bucket Challenge on ‘Late Night With Seth Meyers’ (Video)

Silly? Of course, but don't tell that to 86-year-old Ethel Kennedy, who made a splash and then challenged President Obama (he declined, but donated). And you can't argue with results. The ALS Association reports that it has received $4 million between July 29 and Aug. 12, compared to $1.12 million during the same time period last year, and added 70,000 new donors.

“We have never seen anything like this in the history of the disease,” said Barbara Newhouse, president and chief exective of the ALS Association. “We couldn't be more thrilled with the level of compassion, generosity and sense of humor that people are exhibiting as they take part in this impactful viral initiative.”

Gwen Stefani accepted the challenge from singer Blake Shelton, who will be her colleague when she joins NBC's “The Voice” next season. After absorbing an excruciatingly slow pour by the country crooner, she challenged her husband Gavin Rossdale, Nicole Ritchie and Jessica Alba.

Media moguls got in on the action, too. After Facebook founder Mark Zuckerberg took the plunge — self-inflicted, at that — he challenged fellow billionaire Bill Gates to do his part. Not surprisingly, the Microsoft founder agreed to go under, but not before engineering a special contraption for his big splash.

Even though he donated, President Obama may not be off the hook yet. Both hoopster James and Bieber challenged him, and so did Weird Al Yankoivic, who also pitched the Dalai Lama and the pope.

Watch Hollywood get soaked for a good cause. Who's next?