A/N: The crack!fic plot bunnies wouldn't leave me alone.
Alas, I own nothing. Doctor Who belongs to some rich guy and Charlie the Unicorn belongs to the internet.
"Put a banana in your ear! Put a ripe banana right into your favorite ear! It's true, so true, once it's in your fears will disappear. The bad in the world is hard to hear when in your ear a banana cheers," the Doctor danced about the control room in the TARDIS, singing at the top of his lungs.
"What on earth are you doing?" Donna blinked.
He pulled a banana from his pocket and put it in his ear, singing even louder, "Put a banana in your ear!"
Slap.
"Donna!"
"What are you singing? That's... awful."
"No it's not. It's true. Bananas are good, Donna. And they're good for your ear, too."
"Doctor, I've had my doubts about your sanity, but this... This just proves it. You're completely mad!"
"Look," the Doctor pulled out a laptop and brought up the Charlie the Unicorn video.
"Glub, glub. Glub, glub. Glub, glub. Look over there, it's a coral reef."
"Oh look it's you guys. And you're floating."
"Charlie, we're scuba diving, Charlie. We're exploring the depths of the ocean blue."
Donna could only take so much. She grabbed the laptop from the Doctor, ran over to the door and threw it into the vortex. The video continued playing, unicorns saying in their bubbly high-pitched voices, "Charlie, we're being pulled into the vortex. Swim away foogoo fish, swim away!"
The Doctor stared at her. "Was that necessary?"
"Yes, Spaceman, you've lost it. Completely."
"You could've just turned it off."
"You would've turned it back on," Donna pointed out.
"That's true..." he smiled. "So true. Once it's in your fears will disappear, the bad in the world is hard to hear when in your ear a banana cheers,"
Grinning, he pulled the banana out of his pocket.
"Donna, you look quite down with your big sad eyes and your big fat frown. The world doesn't have to be so gray. Donna, when your life's a mess. When you're feeling blue, or are in distress, I know what can wipe that sad away. All you have to do is put a banana in your ear–" he put the banana in her ear, smiling at her uncontrollably. "Put a ripe banan–"
Smack.
"Donna!"