Flashback:
Abby and Gibbs were standing in front of the large fridge in her lab.
The bouncy scientist was smiling at her sternly looking boss.
"Secret Santa?!? You can't be serious."
She looked at him as serious as possible.
"I am, now pick a piece of paper."
He couldn't help but smile. She did it again.
"Alright."
He did as told and hoped that he would get her name.
She smiled inwardly.
Part one of her plan was successful, now she hope part two would work out just the same.
She waited till she was sure that Gibbs was inside the elevator before she switched the few pieces of paper in the box, with the other prepared ones.
Now she only had to make sure Tony would get the right name.
Part two of her plan worked just as good as part one, without a hint of hesitation Tony had agreed to exchanged the name he had got.
The thought of calling this whole thing off, was replaced by the confidence that her friends wouldn't be too pissed if they ever found out.
Ducky and Tim had helped her with some parts of her plan and both had promised her, to play along, which included to pretend that they had picked each others name, of course without giving away that they knew who had their name.
( I know this sentence is kind of weird, sorry about that.)