The battle over Proposition 37, a ballot initiative that would require labeling many genetically engineered ingredients, is heating up in California. Large food and biotech companies have put up around $35 million to defeat the initiative, but now Prop 37 proponents have a slew of celebrities on their side.

Danny DeVito, Dave Matthews, Bill Maher and other big Hollywood names all star in a new, sarcastic video in support of the proposition.

“Why would you want to know what’s in your food?” asks Matthews in the online ad, which was produced by Food & Water Watch.

“It’s kind of none of your business,” adds actress Katilin Olson, of popular sitcom It’s Always Sunny in Philadelphia.

“Certain companies would lose a lot of money if you didn’t buy their stuff,” jokes Maher.

The 1:30 spot continues with each celebrity asking California voters to vote Yes on Prop 37 for the “Right to Know” what’s in their food. The campaign is trying to get the “PSA” on air to combat the onslaught of TV ads against Prop 37.

The No on Prop 37 folks – backed by Monsanto, Dow, DuPont, PepsiCo, Nestle and others – argue that labeling would just needlessly increase the cost of food, confuse consumers and open up the floodgates for litigation against food companies and grocers.

“California farmers are threatened by Prop 37, a complex bureaucratic food labeling proposition that would increase costs to food producers and consumers by billions of dollars,” says Ted Sheely, who is identified as a California family farmer. “It’s going to put California at a disadvantage with the 49 other states. The people who are least able to pay are going to have to pay more.”

The U.S. Food and Drug Administration currently only requires labeling of GE foods if they have a significantly different nutritional profile or contain an allergen that consumers would not normally expect to be present. The FDA maintains there is no significant difference between GE and non-GE foods and foods containing GE ingredients pose no risk to human health.

A recent poll by Oklahoma State University found that 76.8 percent of California voters plan to vote “yes” on Prop 37, but the study also found that support for the initiative waned once poll respondents were shown a “No on Prop 37” ad.