Pauley Perrette Pauley Perrette

NCIS star Pauley Perrette live-tweeted Tuesday's episode, which introduced the Port-to-Port Killer, a serial murderer that the team will chase the rest of the season.

CBS kicks off "Tweet Week"

It was a tense hour that saw Gibbs (Mark Harmon) butt heads with Special Agent E. J. Barrett (guest star Sarah Jane Morris) over who should take lead on the sensitive case. Even the burgeoning romance between Ziva (Cote de Pablo) and her finally introduced boyfriend, Ray (Enrique Murciano) turned much more serious than flowers and candlelight

Thankfully, Perrette's tweets — all part of CBS Tweet Week — kept it a little bit lighter. Behold, the five things we were most excited/intrigued to learn.

1. David McCallum does a great baby voice.
In the teaser opening, the killer lures his victim into an alley using a baby doll that speaks with a computerized voice. Perrette quickly informed viewers that the voice was actually recorded by a cast member, and after a few minutes of guessing, she revealed that it was none other than Ducky!

2. What's in the Caff-Pow cup? Perrette's character, Abby Sciutto, is known for her Goth style and affinity for the fictional energy drink. So, what is the actress actually hopped up on during all those takes? "It's CRANBERRY JUICE!" Perrette tweeted. "That's what I drink in my caff-pow cup."

Check out photos of the NCIS cast

3. Perrette's college education comes in handy.
Abby is always able to help Gibbs & Co. find a crucial piece of the puzzle when they're tracking a baddie. Crime-solving is something Perrette has been interested in long before she ever put on Abby's lab coat. "I studied Sociology, Psychology & Criminal Science in college," she revealed.

4. Abby's nickname for the serial killer is probably going to stick. When talking with Gibbs about the Port-to-Port Killer, Abby's over-caffeinated sensibilities lead her to shorten the name to "P2P." Even better, its hashtag ready! "#NCIS Remember that! #P2PKiller!" Perrette wrote.

Exclusive: Meet NCIS' newest team members

5. The eyes have it. The episode ends with P2P sending a message to Ziva and Tony (Michael Weatherly), who end their day at a bar. After Tony surprisingly tells Ziva to ease up on Ray, the bartended delivers a drink from a mysterious patron who's since disappeared. Inside one of the ice cubes in Tony's drink is an eye ball! "HERE'S YOUR SCOOP (your prize for playing)," Perrette tweeted. "THE EYEBALL BELONGS TO SOMEONE YOU KNOW!"

Any guesses who P2P's latest victim is? Did follow along with Perrette's tweets?