One day the Third Doctor was driving through Canada in Bessie when he stopped at a shoe museum. Because Bessie is a car, she had to wait in the parking lot. While the Third Doctor was enjoying shoes, along came Barney the purple dinosaur.
"I love you, I'm creepy, won't you drive away with me?" sang Barney as he walked up to Bessie. He opened the door and climbed in. The Third Doctor walked out of the museum and saw Barney driving away. He held out the sonic screwdriver in the hopes of doing anything to stop Barney from escaping, but it was too late. The Third Doctor chased after them, his black coat billowing behind him.
Meanwhile, Barney drove Bessie back to his secret lair, which was underneath a playground. We're not going to tell you what happened next, just know that the Third Doctor burst in an a very pleasured Barney and a still-an-inanimate-object Bessie.
"BESSIE!" exclaimed the Third Doctor as he attacked Barney. Once Barney was unconscious he got into Bessie and drove away.
The Third Doctor forgot about the incident until several months later, when a small purple car mysteriously appeared next to Bessie.