Joe Biden chided a man about wearing a face mask outside while walking a dog in his first organized appearance on the short-form video app TikTok. . . . "Dave, what the hell?" Biden says to him through the headphones. "I told you to wear your mask outside." The former vice president, 36-year Delaware senator, and presumptive Democratic presidential nominee then appears on the phone screen. "You need to wear your mask outside. I don't care if you're just walking your dog," he said.