My attempt at a common fic cliche. Disclaimer: I don't own Doctor Who.
When River was a girl she– well, she doesn't know what she used to do; she can't remember much of anything from that point in her life. But she assumes she was the kind of child that wanted to do everything, just to know what it was like. She would have put her finger in a light socket, and eaten play-dou, and put all sorts of random objects off the floor into her mouth.
She likes to think Amy would have laughed and encouraged her and Rory would have fretted and amassed a first-aid kit the size of the TARDIS. After all, that was exactly what they were like as children.
Unfortunately for her, the toddler currently on the TARDIS grating, chewing on the sonic screwdriver, was clearly of the same adventurous spirit. River thought about taking the sonic away, like she'd already had to do with a Silurian remote and a miniature yoyo, but the child wasn't animatronic and therefore not in danger of accidently injuring itself with a screwdriver. And Rory had taken to making the Doctor actually clean the sonic when he'd poked it into something nasty, after what happened on Tragudor II. Everything should be fine.
River would feel a bit helpless right now if she wasn't old hat at dealing with people who were impossibly, inexplicably younger than her. She sighed.
"Well, sweetie, of all the times you couldn't keep your mouth shut, you had to pick the planet that uses de-aging as punishment to mortally insult?"
The Doctor waved the saliva covered sonic screwdriver at her and grinned a gleeful toddler grin.