Sen. Bill Cassidy (R-LA) found the segment so moving, he publicly stated that any Republican-sponsored Obamacare repeal bill should pass the “Jimmy Kimmel test” for Americans with pre-existing medical conditions. After the new “Graham-Cassidy” bill, co-sponsored by Cassidy, called those protections into question, Kimmel angrily jumped back into the fray, turning himself into a health care expert in the process.

Yesterday, he published a seven-minute explainer on the legislation, declaring that the “bill most definitely does not pass [the Jimmy Kimmel] test.” He ended with a literal call to action. “It’s more important than ever to call your senators and tell them not to gut American health care,” he said to wide applause.

While Kimmel may be an unlikely policy expert, celebrities have long influenced how consumers make decisions regarding their health, often expertly leveraging their fame to encourage people to take action.

Below, five recent celebrities who have shaped the public conversation around health issues, sometimes for the better and sometimes…well, you’ll see.

Charlie Sheen announces he is HIV positive

After the controversial actor announced he was HIV-positive in 2015, a record number of people scrambled to get tested and learn their status. The “Charlie Sheen Effect” was verified by a study published in the journal Prevention Science. John Ayers, who co-authored the study, said Sheen’s disclosure had an undeniable impact. “Our new study shows not only did Sheen’s disclosure lead people to seek information about HIV prevention, it also corresponded with record levels of at-home rapid HIV testing sales,” he told CNN.

Angelina Jolie reveals her risk for breast and ovarian cancer

In a frank series of op-eds, Jolie opened up how learning she carried the BRCA1 mutation, which she said gave her an 87% risk of developing breast cancer and a 50% risk of developing ovarian cancer, informed her health choices. After her doctors told her there was reason to believe she had an early form of the disease, Jolie opted for surgery in 2015 to remove her breasts, ovaries and fallopian tubes. Her disclosure opened up an important debate about screening and prophylactic mastectomy. Since Jolie went public with her decision, studies have found a dramatic uptick in high-risk patient screenings for the genetic mutation.

Prince Harry opens up about his mental health

While it’s fun to speculate on the love life of the bachelor royal, Prince Harry inspired a different conversation earlier this year when he spoke candidly about his struggles with mental health following the death of his mother, Princess Diana. His decision to seek professional, he says, helped saved him. “I was very close to a complete breakdown on numerous occasions,” he told The Telegraph. Following Harry’s disclosure, which was part of a “national conversation about mental health,” a record number of people reached out for mental health evaluations and services. Mind, Britain’s leading mental health organization had a 38% increase in calls the first week after Harry’s candid revelation.

Jenny McCarthy’s “anti-vaccine” stance becomes part of a troubling trend

By the end January of 2015, the U.S. had logged more measles cases than the country typically sees in a year. This was particularly troubling, as the disease had been declared eradicated in 2000. The bulk of the infections could be traced back to an outbreak in Disneyland; Researchers later determined that “vaccine refusal” was primarily to blame. Actress Jenny McCarthy is largely viewed as the celebrity face of the anti-vaccine movement, which spawned from a now discredited study that linked the MMR (measles/mumps/rubella) vaccine to autism. Let’s be clear: researchers have confirmed that such a connection does not exist, but that hasn’t stopped anti-vaccine activists from frightening parents for more than a decade.

Gwyneth Paltrow’s status as a wellness guru is unclear

The Academy-award winning actress has used her fame to launch Goop, a lifestyle brand that offers New Age-y, mostly benign content and advice. Recently, however, Goop’s wellness claims have come under fire. This August, Truth in Advertising (TINA) announced that it found “50 instances in which the company claims, either expressly or implicitly, that its products (or those it promotes) can treat, cure, prevent, alleviate the symptoms of, or reduce the risk of developing a number of ailments.” Subscription-based supplements and stickers that claim to reduce anxiety were among the problematic products. Long before the controversy hit, Goop was peddling questionable health advice. For example, the company recommended a procedure known as “vaginal steaming” that promised to “cleanse your uterus.” The site also sells expensive jade eggs that, when inserted into your vagina, are supposed to “increase vaginal muscle tone, hormonal balance, and feminine energy in general.” The $66 item sold out, according to The Washington Post, though Dr. Jen Gunter, an OB/GYN for Kaiser Permanente in San Francisco, told the Post the whole thing was “the biggest load of garbage.”