Heey KR Fans! We will talk about the Knight Automated Roving Robot, a.k.a. KARR, who will appear in the original series and the new series and that is also the reason why we are going to talk about

Knight Automated Roving Robot (original series)

KARR is a malignant prototype of KITT. He appeared in two episodes of the original series: Trust Doesn't Rust & KITT vs KARR. KARR stands for Knight Automated Roving Robot.    

KARR was Wilton Knight's first attempt to build a Super Car. But thanks to a programming error, KARR can only think about himself and therefore he is a danger to everyone. The biggest difference between KITT and KARR, is that KITT protects the life of the human and above all the life of his driver. KARR, on the other hand, protects his own 'life'. After KITT was built, KARR would be dismanteld, but this never happened.
At long last, KARR will be destroyed in the episode "
KITT vs KARR". KITT uses his Turbo Boost against KARR and KARR explodes. But at the end you can see that KARR's scanner is still active... And this proves that KARR is indistructable.  

  

Knight Auto-cybernetic Roving Robotic-exoskeleton

KARR is mentioned in the new Knight Rider series episode "Knight of the Living Dead", and is said to be a prototype of KITT. The KARR acronym now stands for "Knight Auto-cybernetic Roving Robotic-exoskeleton" and instead of an automobile, a schematic display shows a humanoid-looking robot with wheeled legs that converts into an ambiguous off-road vehicle. When KARR finally appears in the episode "Knight to King's Pawn", he takes a form similar to KITT as a 2008 Ford Shelby Mustang GT500KR, but has an amber-colored scanner. Similar to the original character, this KARR had an AI that was programmed for self-preservation, and he was deactivated and placed in storage after he reprogrammed himself and killed seven people.

In the episode, a spy infiltrates the Knight headquarters and activates a self-destruct program within KITT, placed there secretly by Dr. Graiman. In order to save KITT's operating system (which is given priority over his memories), Michael and Sarah transmit the files to the back-up computer at the headquarters, but the transmission is also intercepted by an unknown third party. It is stated that KITT, KARR and the base back-up computer are the only systems able to run the program, and leaves Dr. Graiman with only one conclusion: KARR is still out there, and someone is trying to reactivate him.

KARR returns in the episode "Knight to King's Pawn", with Peter Cullen reprising his vocal role. A pre-recorded message from Dr. Graiman reveals that Mike was KARR's driver and his memories were erased after KARR became uncontrollable. He says that he knew of and opposed Alex Torres and the NSA's plans to reactivate KARR, as they wrongfully believe KITT's artificial intelligence will overwrite KARR's programming flaws. During the dismantling of the SSC (FLAG's control centre), KITT's A.I. chip is removed and delivered by Torres to the NSA, where it is installed into KARR. Mike vows to end this once and for all, and infiltrates Area 51 to rescue KITT, using another chip built by Billy. KARR activates himself, viewing the re-activated KITT as a threat that must be terminated. Alex states that he is now in charge and KARR must take his orders; KARR agrees, but then merges Alex with him as a driver to seek out Mike.

KARR seems to believe that it is his destiny to merge with Mike as before, and comes after KITT to destroy him and get Mike back. Despite KITT lacking his transformation protocols and weapons, Mike takes him into battle anyway. Using a grappling hook, Mike and KITT pull out KARR's chest plate, freeing Alex, and Turbo Boost through his body, destroying him in a way similar to how the KARR of the original series was destroyed. Given the short nature of the battle and the ambiguity of KARR's fate, it is possible that the new KARR might return yet again, although in the following episode entitled "Exit Light, Enter Knight" Mike is told that the KARR project has been permanently abandoned. Strangely, despite KARR's acronym being "Knight Auto-Cybernetic Roving Robotic-Exoskeleton" in "Knight of the Living Dead", in "Knight to King's Pawn" Billy refers to him using the original "Knight Automated Roving Robot"