Tonight Show With Jimmy Fallon December 13, 2019 1:44 am ‘Tonight': Trump Goes After Greta Thunberg In his monologue, Jimmy Fallon jokes about President Donald Trump going after 16-year-old climate activist Greta Thunberg, SantaCon and the latest impeachment hearings. US & World Videos 1:07 Britney Spears spotted as authorities respond to alleged hotel incident 2:15 Prince William and Kate Middleton ‘going through hell,' friend claims (report) 8:01 Lady Gaga's outfit changes, Rihanna's bold looks and more iconic Met Gala moments 2:48 Taylor Swift fans react to Jake Gyllenhaal and Sabrina Carpenter's ‘SNL' appearance 5:57 Why your monthly horoscope for May is looking lucky