NCIS is a CBS crime drama that has been on the air for over sixteen years. Through that time the show has seen its characters enter into a number of both platonic and romantic relationships with each other, usually starting as merely coworkers with bonds developing over time.

Not all friendships have the same amount of chemistry, resulting in some of these friendships being stronger and with better chemistry than others. Some are so lacking in chemistry that they detract more from the story than add to it. In that spirit, here are the five best friendships of NCIS, and the five worst.

Worst: Cassidy and DiNozzo

Special Agent Paula Cassidy was first introduced when Gibbs and his team were investigating a death at Guantanamo Bay. She met Very Special Agent Anthony DiNozzo while both were on the job and subsequently developed a short-lived romantic relationship. She eventually broke it off with DiNozzo, though her reasoning was unclear. She later acted as a temporary replacement for Kate Todd after her death, and her interactions with Tony showed a strained relationship.

The couple’s chemistry was virtually nonexistent from the start and only got worse after their breakup. Tony still grieved Cassidy’s death later in the series with the rest of the agency, which was the most genuine emotion he showed toward her.

Best: Ducky and Palmer

Dr. Donald Mallard, or Ducky, and Dr. Jimmy Palmer both acted as Medical Examiners for NCIS in Washington, D.C. Jimmy took over as Ducky’s assistant after Gerald left NCIS due to being injured by terrorist Ari Haswari. The two first started out with a teacher-student relationship, as Jimmy was still in training.

As Jimmy became more competent, he and Ducky developed a closer bond, with Ducky congratulating Jimmy and calling him “Dr. Palmer” upon learning he passed his Medical Examiner tests. Jimmy even named his newborn daughter after Ducky’s late mother. Jimmy is now the full-time medical examiner, with Ducky now acting as a part-time NCIS historian.

Worst: Kate and DiNozzo

Special Agent Kate Todd and Anthony DiNozzo’s relationship was often described as having a sibling dynamic. However, the dynamic between the two, for the most part, was overly antagonistic, even for siblings. The two had their moments, like when DiNozzo contracted the pneumonic plague, and Kate stayed by his side for as long as she could, and DiNozzo later grieved her death with the rest of the team.

Other than that, the two were more caricatures of a sibling dynamic, needing very little provocation in order to start bickering or pranking one another.

Best: Abby and Kate

Abby Sciuto and Kate Todd were friends both in and out of the office. The two were depicted as having girls’ nights and knew the most about each others’ personal lives. Abby even knew what and where Kate’s tattoo was, which was never actually revealed in the show. Kate, a skilled artist, also drew sketches of her teammates, including Abby, who was depicted as a bat. Abby loved it and kept it in her office.

Abby was one of the characters who took Kate’s death the hardest and consequently was the most skeptical of Ziva David joining the team.

Worst: Abby and Clayton Reeves

This friendship could have been great, had it not been short-lived. Through much of his time working at NCIS as an MI6 liaison, Clayton Reeves kept mostly to himself but later was shown to have grown close to Abby. In their second to last episode on the show, Abby and Clayton go to dinner together, and Clayton is killed later that night in an effort to protect Abby. In his and his late mother’s honor, Abby leaves NCIS to start a homeless charity in England.

The two had great chemistry, but their friendship could have been more developed, had the two not been written out of the show.

Best: DiNozzo and Director Shepard

After Agent Gibbs was injured in an explosion, he took some time off, putting DiNozzo, the senior-most member of the team at the time, in charge. During that time, he worked closely with Director Jenny Shepard and was even assigned to work an undercover assignment for her. The two became close during this time and eventually were on a first-name basis.

What was so great about this friendship was that it was strictly platonic, with no clear implication of anything romantic or sexual developing between the two, which is especially rare for DiNozzo.

Worst: DiNozzo and McGee

While DiNozzo and McGee have shown to have some respect for one another, most of the time, their relationship is depicted as having a sibling dynamic, similar to DiNozzo and Kate. This sibling dynamic is less overtly antagonistic than DiNozzo and Kate’s, but there is still a level of antagonism, mostly shown through pranks, trying to one-up each other, or take sole credit for work they did together.

At times, it seemed that DiNozzo would still try to undermine McGee by calling him “Probie” or creating a pun on his last name such as “McGeek,” even long after McGee established himself as a good agent, making the friendship not the greatest.

Best: Gibbs and Fornell

Special Agent Gibbs of NCIS and Agent Fornell of the FBI often fight over jurisdiction when their paths cross on cases. That, and the two having a mutual ex-wife, Diane Sterling, cause their relationship initially to appear as a strained one. However, as the series progresses and their characters develop, Gibbs and Fornell form a strong dynamic and a close bond.

Their friendship is often used for moments of comic relief in an otherwise serious show. Fornell is not in every episode, but that makes his appearances, and his and Gibbs’s antics, more narratively interesting.

Worst: Gibbs and Director Shepard

When Director Jenny Shepard was first introduced in the show, it was immediately established that she and Gibbs had a past sexual, and possibly romantic, relationship. This aspect of their relationship was often brought up, especially during points of conflict between the two characters.

While it does seem that the two did truly care for each other and respect each other, it seemed that the main purpose of their interactions in the show was to add conflict. This made Director Shepard especially a mere plot point for Gibbs. Thankfully, Shepard’s relationships with other characters provided her with opportunities for character development.

Best: Abby and McGee

Abby and McGee’s relationship started as flirtatious and evolved into a casual, sexual fling. However, that storyline was quickly abandoned, but they remained close friends with each other. Abby and McGee spent many cases in her lab running tests on evidence and hacking computers in order to better pinpoint suspects.

While both initially were jealous of the others’ romantic partners, they both grew accepting of them, with Abby even being ecstatic about McGee settling down and having a family with his wife, Delilah. The fact that the two were able to remain close and ultimately not affect each others’ personal lives due to their history with each other makes their friendship the best of the NCIS characters’ friendships.

Next: NCIS: 10 Best Episodes (According to IMDb)