Calvin flipped a switch on his new invention.
This particular switch would throw the invention and its wearer into a universe selected via telepathic interface.
When Calvin flipped it though, the invention was thrown into a universe without its wearer.
In the TARDIS, a small glove-like object materialized inside the Time Rotor.
"Uh, Doctor? Why is there a glove in the time rotor?" Martha asked.
Back in Calvin's room, there was an unmistakable VWOOOOORP. VWOOOOORP. as a Type 40 materialized, and as River would put it, "you leave the brakes on."
Calvin immediately ran to the closet and fumbled around with a bow tie.
The Doctor and Martha exited the TARDIS.
". . . you look ridiculous," the Doctor pointed out.
"What? Whaaaaat?" That from Martha.
"What? Bow ties are cool! And you are not." Ahh, Calvin.
Martha pretty much exploded. "Of all the universes to land in, of course I land in the one with an insane kid aND A CARDBOARD BOX!"
Calvin looked puzzled for a moment. "Oh. Right. Comic strip."
The Doctor tried the standard introduction routine. "Hello! I'm-"
Calvin cut him off. "The Doctor, from the planet Gallifrey in the constellation of Kasterboros, on his eleventh regeneration who everyone calls the Tenth because the ninth who everyone calls the 8.5th saved Gallifrey by locking it in a painting called Gallifrey Falls No More and wiped his memory of it to avoid influencing future action by his eleventh, thirteenth and fourteenth selves who everyone calls the Tenth, Eleventh and Twelfth on the Time War. He travels with a companion, usually female, in a Type 40 TARDIS stuck in the form of a police box after landing in the 76 Totter's Lane junkyard near Coal Hill school back when he was 400 or so." Calvin blinked. "I said too much, didn't I?"
"Yeah, you did. She's-"
"Martha Jones, medical student, got her research hospital transmatted to the moon by the Judoon, left on one of your adventures just in time to miss the vote where the Master, a renegade Time Lord who escaped the Time War, was elected Prime Minister under the alias of Harold Saxon. The Master then attempted to assist the Toclafane, robotic shells for the race known to the year 13,000,000,000,000 as Futurekind, to create a 13-trillion-year empire. Slight smashing up of your Type 40 reversed the changes to the timeline. She later saved the Earth during the incident with the reality bomb. That pretty much sums it up."
"Wait, in the previous rapid-talk explanation, you said fourteenth?"
Calvin smirked. "Spoilers."
"You're impossible..."