"Doctor, you're off your rocker! What happened to time paradoxes and messing up lives and changing timelines? Not to mention she'll know it's you!" shouted Donna.
"Donna, don't argue. Humans get all flustered and red and swollen looking when they argue. Trust me, it's not pretty. Besides she can't possibly know it's me. I've regenerated, plus I'm going back to a time BEFORE she met me. I'll just be a random stranger. A very strange stranger," the Doctor answered.
"A very strange snogging stranger," Donna replied.
"Donna, time lords don't 'snog', human teenagers do," the Doctor replied, as if it was the most obvious thing in the world.
"Blimey, and you don't think she'll figure it out later? I mean after she's met you? Well met you again…met you officially? When she knows it you…don't you think she'll…know it's you? Won't that be bad or something?"
"Donna, I'm sure whatever you just said has some sort of reasoning hiding somewhere in all that confusion and ambiguity, but I'm quite certain this will work."
"So you're gonna do it, and it's gonna work?"
"Correct-a-mundo," the Doctor said, and then grimaced as if he'd just thought of something terrible for the first time.
"What's wrong? Did you just realize that if you do this we'll all die or disappear or Rose will develop some fear of strangers and never get in the Tardis with you in the 'future' and then all those worlds and people you saved will all be dead and the entire universe will be altered because you thought you'd just pop in for afternoon tea or what?" Donna asked, starting to panic.
The Doctor looked up at her with an expression that was a mix between "what are you talking about?", "you're barking mad, you know that?" and even a little bit of "I find your enthusiasm wonderfully refreshing" and replied, "Oh, no, none of that…stuff. I just swore I'd never use that word again—correct-a-mundo. Oh, there I've gone again!" he said and smacked his hand down on the Tardis' console.
"Oh, sorry!" he said caressing the console after the Tardis shuddered in protest. Then he turned to his current companion and grinned ear to ear.
"Shall we?"
Donna just rolled her eyes and collapsed into the chair she had previously vacated in her rush to prevent the world from ending because the Doctor had a hankering for some chips and a blonde. Men, she thought.