The Big Bang Theory hit the midway mark of its sixth season last week with “The Egg Salad Equivalency,” so we’re taking stock of the gang and where they are in their gloriously geeky relationships.

Leonard & Penny

Considering their turbulent past, The Big Bang Theory‘s most enduring on-again-off-again flame has been relatively stable in season 6. (That is to say, they haven’t broken up!) The main problems the two have is potential romantic interlopers, though Penny’s lukewarm feelings about their present and future have presented issues as well.

In spite of her hesitancy early in the season, Penny isn’t beyond feeling a bit possessive of her nerdy boyfriend. Enter Alex, Sheldon’s attractive and unsubtle assistant, of whom Penny made her jealousy quite clear. Until making her feelings neon-level clear in “The Egg Salad Equivalency,” Leonard was oblivious to the fact that Alex actually was romantically interested in him. Though Leonard wasn’t interested in Alex, he was (perhaps excessively) flattered by her attention, which in turn upset Penny, though after a (sort of) cello-accompanied apology, Penny softened and later confessed to Leonard that she often felt insecure about her lack of scientific smarts, as Leonard experienced insecurity about his looks.

Dr. Hofstadter hasn’t just been a bystander in the drama-causing department, however. Leonard was supportive of Penny’s decision to began taking college courses again, but in all the wrong ways, leading to disappointment between them. He also developed his own prickly patch of jealousy over Penny’s interactions with cute British classmate Cole, which Penny found both irritating and insulting.

But ultimately, it was that jealousy which ended up facilitating a high point in the couple’s relationship so far. As Penny reassured Leonard that he had nothing to worry about, she blurted out the words which she had previously been determined not to say. “You know I love you!” she said, as though it were the most natural thing in the world, and though the pair decided to downplay the moment, it was a touching – and reassuring – moment both for Leonard and fans who have been supporting the couple throughout the show.

Sheldon & Amy

Like Leonard and Penny, Sheldon and Amy have been taking baby steps down Romance Road in season 6. In the season premiere, the couple celebrated their second anniversary (has it been that long already?) but disaster nearly struck when their contractually-stipulated dinner date was interrupted by Raj – at Sheldon’s invitation. Thankfully, some last minute words-from-the-heart (and Spiderman) saved the day for Sheldon and Amy.

Amy’s devotion to their relationship (and keeping Sheldon devoted) has been a theme in season 6. According to Amy, she and Sheldon will be married in four years (which we think is optimistic, but go for it, Fowler) and perhaps as part of her game plan, Amy continued to advance their couplehood wherever possible. Halloween proved to be a middling success in this case, as she and Sheldon were semi-coordinated as as Raggedy Anne and “Raggedy C3P0″ – it’s no Blossom and Joey, but at least she got the wig on him.

Amy also attempted to nudge Sheldon into more consistently boyfriend-like behavior, dropping hints (…sure, let’s call them “hints”) that he should side with her over his Fun-With-Flags friends. It took a little intervention from Penny (and Long Island), but Sheldon ultimately complied – albeit with a certain amount of bemusement.

But perhaps the biggest step in Sheldon and Amy’s relationship was Amy’s almost shocking success at wheedling some sexual satisfaction out of Sheldon. Sure, she had to get the flu to do it (and then milk that virus for all it was worth) but in her bizarre, almost creepy way, Amy managed to get some physical attention from her famously fussy boyfriend. Can true love be far behind?

Howard & Bernadette

As the newlyweds of The Big Bang Theory, the Wolowitzes might have expected a little romance and private time at the beginning of their marriage. But (this being The Big Bang Theory) things went just a little bit differently for the unlikely lovebirds, and wedded bliss has not been quite so easy to come by – though it has been hilarious.

Season 6 began with Howard rocketing to outer space – about as far away from his new wife as possible. (Which is impressive even for Howard, we think.) Skype kept the two in touch, though communications began to break down as Howard’s time in the stratosphere wore on, especially as it became clear that Astronaut Wolowitz had told his mother that he and Bernadette would live in her house, while promising Bernadette that he would move out into her place like a real, grown-up husband.

The Ma Wolowitz situation came to a head upon Howard’s (somewhat lackluster) return, when Bernadette insisted that Howard move into her apartment. He complied after dragging his heels a bit…only to have Bernadette turn around and move him right back in with his mother after indulging in a touch of nostalgia.

Bernadette’s parents also presented a hurdle for the newlyweds. Bernie tried to facilitate a little familial bonding between Howard and his taciturn father-in-law, which both men powerfully resisted. Happily (though ironically), the two did find common ground over the prospect of a forced fishing trip, which turned into a much more pleasant weekend spent shooting craps.

Raj

Oh, Raj. What is there to say? The Big Bang Theory‘s lovelorn fifth wheel hasn’t had much luck with the ladies this season, we’re afraid. On the bright side, Howard’s atmospheric adventures left Raj with an opening for a new ‘bro,’ which turned out to be filled quite happily with comic book store owner Stuart. Even with Howard’s return, Raj and Stuart have continued to enjoy borderline-romantic outings, throwing Halloween parties, and spending comfortable evenings together. (Congratulations?)

But Raj hasn’t given up the hunt for Ms. Right, though he remains frozen-tongued around women unless saturated with alcohol. Penny, Amy, and Bernadette’s attempts to set him up at a bar failed due to Raj’s bizarre standards…though he may have walked away from the evening nursing a crush on Amy. Raj has also recently confessed to laying the groundwork for eventually seducing Alex, but given her preference for Leonard and his selective mutism, we’re not yet convinced that this is a perfect match.

But hey, Raj, surprise us, buddy. We know you’ve got it in you!

What do you think is in store for our favorite couples?