Roads to Vegas (S11E21)

Brian wins tickets to see Celine Dion in Las Vegas. As they prepare to travel, Stewie decides to try out his new teleportation machine. After it appears to have malfunctioned, he believes it has failed to work. But instead, it created a duplicate set of Brian and Stewie. While one pair flies to Las Vegas, a duplicated pair find themselves transported as originally planned. (BBC)