It.
The Doctor bounced into the console room, all shiny eyed and wide grin, bobbing on the balls of his feet where he stood.
"River I have something really important to tell you." She looked up curiously.
"Yes sweetie?"
"It's very extremely important. You must listen very carefully. Give me all your attention." She laughed.
"What is it?" He grinned and lunged forwards tapping his wife lightly on the shoulder.
"You're it!"
River watched as her husband giggled like a child and bounded down the hall way into the Tardis.
"Oh you are in so much trouble!" She grinned, dropping the scanner that she was holding to sprint after him. She saw the tail of his coat swish round the corner and she leapt after him, grabbing him by the hand. She yanked him towards her and planted a quick kiss on his lips.
"You're it," she grinned, the turned to sprint further into the Tardis, her husband hot on her heals.