Williams, 41, stopped by Jimmy Kimmel Live! on Wednesday evening, May 7, and engaged in a fierce competition with the talk show host, 46.
Kimmel challenged the "Happy" singer to a "Twofie Shootout," where each star hit Hollywood Boulevard and tried to take as many selfies with strangers on the street as possible in 30 seconds.
The late-night funnyman counted a total of 10 twofies and got a cameo from Darth Vader, who was posing on the boulevard.
Williams kept it cool, moseying along the street and snapping a total of six twofies.
Watch the hilarious video of Kimmel and Williams above!