This article may contain spoilers.

Welcome back to reality ... Eureka-reality that is. For, as you know, nothings normal in Eureka. And just when you thought things could not get anymore weirder in a town which has already had two suns, a time-loop, and a flesh-eating virus, it did.

"Your Face or Mine" starts off innocuously enough with Jo passing her bi-annual physical/psych test with flying colors, but things start to get really odd when Jo lets down her hair and begins singing Making Whoopee while sliding across a piano top in a red slinky dress. At this point, you probably began to wonder what alternate universe they had slipped into this time. But that is not even close to what happened.

Because Carter was tied-up with his annual certification testing (which Jo had aced with a "perfect" score and Carter felt competitively-pressured to beat), Jo volunteered to be the guinea pig for a new DNA screening security system.

Naturally it did not go smoothly and the next thing we know is Jo is acting distinctly not like her self. One minute shes spouting Isaac Asimovs three laws of robotics; and the next shes barely able to distinguish that knowledge, motive and opportunity equal a crime trifecta -- or most tellingly, she said in her own words, I took a nap and now I feel like a brand new woman.

It looked like the same Jo that we know and love, but her behavior and personality was decidedly not that of Deputy Jo Lupo. It was a Jo-doppelganger.

In what could have been an episode with a serious debate about sacrificing civil liberties for the sake of national security, instead it became an issue of: what makes a person who they are? Is a person merely a sum of their physical parts, or are they something more? Is the essence of who they are consist of their soul, their personality, their physical looks, or a combination of all of these things?

So while Jo struggled with her own identity, we were challenged with the question: how far can you walk in another persons shoes? But, as the shy lab-geek Julia quickly discovered, not very far. For even Zane immediately began to suspect something was awry and puzzledly asked Julia (who was masquerading as Jo): Do I know you? To which Julia mysteriously replied: Maybe you dont.

Thus, confusion quickly arose as to whether Jo had become mentally unstable since she was showing signs of memory loss, aberrant behavior and acting impulsively. It was not until Jo actually came face to face with Julia (looking exactly like Jo), that Jo saw through the DNA-ruse that Julia had concocted.

Alas, Julia was one step ahead and moved to discredit Jo by changing Jos DNA so Jo looked like Julia. Unable to determine who was the actual Jo and Julia, it was only through a rigorous questioning by Zane -- which ultimately boiled down to boxers or briefs? and Jo responded, yours or mine? -- that Julias nefarious DNA manipulation was discovered.

Henrys solemn resolution that alls well and ends well after GD granted Julia probation for her unscrupulous identify-theft seems a bit too pat of an ending. But at least this time Fargo finally got the girl!

What Worked

This episode showcased Erica Cerra beautifully as she was able to show off a variety of facets not seen before: she sang like a nightingale, look like a super model and pulled-off a wickedly comedic version of herself.

It also brought out a surprisingly touching side of Fargo, which is rarely seen and was delightful to behold. His explanation to Julia, that she had him at Halo and that the only reason he did not see her feelings for him was because he was clueless and socially awkward, had me misty-eyed.

It was also highly entertaining watching Carter try to push that blasted red button with only the use of a deck of cards, a handful for blue straws and a panic button. Also, his belief that the disappearing floor was a hologram and then falling into it was hysterical. And capping it all off was Jos comment to him when he concluded the testing: It could have been worse, there could have been two of you, was priceless.

What Didn't Work

It felt like both Jo and Carter were under investigative-handicaps since they were not able to bounce ideas off each other. For example, the scene where Jo wanted to talk to Carter, but was not permitted to do so because he was still in the midst of the psych testing only emphasized that they are but one-half of a carefully balanced crime-fighting duo.

Thus, next week it will be nice to see things return to Eureka-normal with Jo ready to take down criminal wrong-doers with a flick of her pinky and Carter ferreting out impossible answers with razor-keen instinct and investigative skills.

Giving Credit Where Credit Is Due

"Your Face or Mine" was written by Jaime Paglia and directed by Colin Ferguson. Eureka" stars Colin Ferguson, Salli Richardson-Whitfield, Joe Morton, Jordan Hinson, Erica Cerra, Neil Grayston, Chris Gauthier, Ever Carradine and Niall Matter.

"Eureka" airs Fridays at 9pm on Syfy.