RAINDROPS KEEP FALLING ON MY HEAD.

Tim walks from the back elevator to his desk, sits and resumes working on his computer.

"What took you so long McSlowbie?" queries Tony from behind his. "These cold cases won't review themselves ya know."
Across the bullpen their new colleague has tuned out their typical bantering and is deeply immersed in the case file she is reading.
"I was trying to help Abby with Major Mass Spec."
"Trying McMIT?" Tony grins.
"Neither of us could work out what the problem was. Abby had to call in a technician. She said she'll have to take a rain check on..."
"Brain check?" Ziva asks with a note of alarm in her voice. "Is Abby ill? Does she need to have tests done? Oh. Gibbs will not be happy about this and a grumpy Gibbs..."
"Not a brain check Ziva. A rain check." Tony says trying not to sound exasperated at another misheard or misunderstood expression and only just succeeding.

Ziva glances at the windows where bright sunshine is streaming through.
"But there is no rain and I do not think any is forecast."
Tim starts to chuckle then hastily turns it into a cough as she turns her gaze to him.
"Something in my throat."
"Taking a rain check simply means our mistress of the lab cannot come to lunch with us today but hopes to another time."
"Ah. Thank you for the explaining that to me Tony."
"Shall we go then?"
"Yeah."
"Okay."
The three shut down their computers, gather their gear and head out for lunch. As they step into the elevator Ziva asks "Who pays when lunch is a rain check?"
Tony and Tim lock eyes for a moment then smile before replying in unison.
"You do."

Of course they know this is not true but are upholding the long-standing NCIS tradition of pranking the newbie. She smiles back at them. Lunch would be a small price to pay as a way of starting to become an accepted member of the team.