Episodes: "The Man in the Morgue"; "Judas on a Pole"; and 22 more.

What Made Her Memorable: Everything gets funnier and more interesting whenever federal prosecutor Caroline Julian appears. Her tolerance of the "squints" and her trust in Booth make Caroline the character most deserving of a promotion to series regular.

Episodes: "The Hero in the Hold"; "The Witch in the Wardrobe"; "The Boy with the Answer"; and "The Bullet in the Brain."

What Made Her Memorable: A serial killer who kidnapped Brennan, Hodgins and Booth -- and almost got away with it -- became even creepier when the audience found out she was a U.S. Attorney who had been working with the team all along. Her identity was concealed for two seasons, making her scarier than any other BONES killer.

Episodes: "The Goop on the Girl."

What Made Her Memorable: When Brennan's long-lost cousin showed up for Christmas, the real-life sisters’ resemblance and their character similarities proved hilarious every time they were on screen together. The two characters immediately disliked each other, especially since Margaret constantly quoted Ben Franklin.

Episodes: "The Girl in the Gator"; "The Man in the Mansion"; "The Priest in the Churchyard"; "Mayhem on a Cross" and "The Dwarf in the Dirt."

What Made Him Memorable: After this psychiatrist was assigned to evaluate Booth, his hilariously honest observations pushed Brennan and Booth to uncover some truths about their partnership. He always brings an entertaining and humorous contrast to Bones serious nature.

Episodes: "Judas on a Pole"; "Killer in the Concrete"; and 12 more.

What Made Him Memorable: Max showed up as Brennan’s absentee, convict father, but soon became a valuable resource of criminal information for the team. He always strikes the perfect balance between menacing and caring, showing Brennan that the father she remembers from her childhood is still there.

Episodes: "The Bullet in the Brain"; "The Killer in the Crosshairs"; "The Hole in the Heart."

What Made Him Memorable: Jacob Broadsky was the anti-Booth: an Army sniper who thought he was doing the justice system a favor by killing criminals. His unwavering belief, combined with the meticulous nature of his attacks, made him extremely dangerous.

Episodes: "A Man on Death Row"; "The Blonde in the Game"; "The Man in the Cell."

What Made Him Memorable: As Brennan’s first real nemesis, Epps played endless psychological games with Booth and Bones, even forcing Temperance to kill someone. His genius surpassed Brennan’s and set the standard for future enemies of the Jeffersonian team.

Episodes: "The Girl in the Gator"; "The Man in the Mansion"; "The Bodies in the Book"; "The Boneless Bride in the River."

What Made Him Memorable: Sully was Brennan’s temporary partner and love interest, and they had palpable chemistry. He was endlessly charming, funny and ridiculously good looking, three characteristics that made him the only man who could have ever replaced Booth and been accepted by fans.

Episodes: "The Death of the Queen Bee."

What Made Him Memorable: Brennan’s only high-school friend, weird janitor Ray Buxley, was the personification of creepy -- a man who is surrounded by knives and has made the crazy stare into an art form. The comedy comes when Brennan can’t understand why everyone else finds him disturbing.

Episodes: "The Body and the Bounty."

What Made Him Memorable: Intern Bunsen Jude -- "the Science Dude" who was a cross between Bill Nye and Mr. Wizard -- brought fun to the various scientific processes and proved to be one of the smartest and quirkiest interns Brennan has ever had. In the end he reminds Brennan why she loved science to begin with.