John Oliver turned to a cadre of beloved Hollywood stars to help him with an important mission. The Last Week Tonight host returned on Sunday with an expose on the prevalence and spread of coronavirus conspiracy theories, and tasked some widely trusted public figures — including Paul Rudd and John Cena — to help get his point across.

After spending the better part of 20 minutes intricately debunking the most popular conspiracy theories circulating online about the virus, Oliver made a passionate plea for his viewers to try and combat the spread of these dangerous rumors.

However, Oliver explained that science has shown that confronting people, shaming them for their beliefs, or trying to prove to them they are wrong will only strengthen those people’s conspiracy-minded views. Instead, it’s important to be compassionate, and encourage people to ask questions for themselves.

So, to appeal to grandparents and older citizens who might be spreading fake coronavirus news, Oliver turned to the man who “they’ve been letting into their home every week night to calmly tell them what is or isn’t correct” — Alex Trebek.

“If nobody ever asked questions, Jeopardy! would be a very, very, weird show, wouldn’t it?” Trebek asked, as part of a PSA he shot for Last Week Tonight encouraging people to be more curious about the world around them, and to be cautious about believing what they read online.

Oliver also got Cena to record a similar PSA for coronavirus conspiracy theorists who like “wrestling or Fast and Furious movies.”

Other PSAs were taped by the Ant-Man star, Pose’s Billy Porter, and Schitt’s Creek star (and comedy icon) Catherine O’Hara, who all addressed the issue with humor, humility, grace and compassion, to get through to people who need to hear the message.