"So, I'm just checking," sighed Nyssa. "Tegan is not pregnant with your child, correct?"
"Yes, of course!" said the Doctor.
"But what were you talking about then?" asked Adric.
"And what about this note?" asked Nyssa, fishing it out of a pocket and handing it to the Doctor. He and Tegan looked at it and paled, looking at each other and blushing.
"I've never seen this before in my life!" exclaimed the Doctor.
"And I don't want to see it again," muttered Tegan.
"But who wrote it then?" asked Adric.
"I'm not sure, but I think I figured out a motive," said the Doctor, tapping a display. "It's -309751.7926496703, or in Earth time, April 1st, 2013."
"April Fool's Day?" groaned Tegan. "That explains a lot."
"What's April Fool's Day?" asked Adric.
"An Earth holiday where it is custom for people to pull pranks on one another, usually revealing it afterwards by exclaiming-"
"April Fool's?" asked Nyssa, pointing at the scanner. Sure enough, the scanner was displaying the words 'April Fool's!' in bright red letters.
"…Well," said Tegan. "That explains what happened to my shampoo."
"Actually," said the Doctor sheepishly. "April Fool's!"
Bloody: Bored! It was either this, or shoot a wall, so I wrote this. Viola.
Unicorn: She doesn't own Doctor Who.