The Scottish actor and his former sidekick Billie Piper attended the Wizard World Comic Con in Philadelphia while Tennant's Time Lord successor Smith headed Down Under with his former co-stars Freema Agyeman and Alex Kingston for the Whoniverse Five City Tour in Australia.
Tennant and Piper began the good-natured competition by sending Smith a video from backstage at the convention, in which Tennant says, "We're killing it up here in Philly... I think they prefer us to you. That's very much the vibe that we're getting. But you know, do what you can out there and we miss you very much. Have fun."
In retaliation, Smith and his female stars recorded a message from onstage at a panel discussion with a crowd of fans yelling in the background. He says, "Tennant, Piper, hello. We see your video and we raise your video dude... we're in Australia mate!"
Tennant responds in a new video, saying, "Matt, Freema, Alex, so you sent a video from your Australian convention - 'oh look at us we've got thousands of friends here' - all cheering and whooping and showing off. Well I'm in Philadelphia and behind these walls is all of Philadelphia, about 4.5 million people ready out here to tell you how popular we are... but I don't need to show you that."
Tennant played the Doctor from 2005 until 2010, when Smith took over for three years.