The conclusion of Season Five of The Big Bang Theory saw Howard (Simon Helberg) and Bernadette (Melissa Rauch) get married, just before Howard was scheduled to go into space to work on the International Space Station. As Season Six begins, Howard is still in space, communicating via computer with Bernadette and his friends. Leonard (Johnny Galecki) and Penny (Kaley Cuoco) are still together, but Penny is having some doubts about their relationship, especially since Leonard surprised her with a marriage proposal. The odd relationship between Sheldon (Jim Parsons) and Amy (Mayim Bialik) continues to grow, as Amy often finds ways to coerce Sheldon into dates or physical contact. With Howard gone, Raj (Kunal Nayyar) becomes close friends with Stuart (Kevin Sussman), the owner of the local comic book store. Once Howard returns from space, things get back to normal with the group, as the three couples continue to navigate bumps in their relationships, while Raj continues to look for love.

When The Big Bang Theory began in 2007, the show's focus was on how nerdy its four male leads were and how none of them could get dates (Well, Sheldon wasn't interested in dating...). Leonard formed an immediate crush on new neighbor Penny and Howard had convinced himself that he was a ladies man, when he clearly wasn't, but otherwise, the guys were unlucky in love. Now, six years later, the show is all about relationships and romance. This change could have easily hurt the show, such as when your best friend starts dating someone and you stop hanging out as much. But, the powers that be at The Big Bang Theory have been able to mine these new storylines for plenty of laughs and interesting situations. Two things make this work. First of all, the show presents these relationships just like any other relationship we've seen on TV, and the couples go through the same ups and downs as everyone else. This sort of familiarity certainly helps. However, secondly, the guys are still geeks and this makes for some funny moments as well. The best moments come from Sheldon and Amy, as their truly bizarre coupling may be the most unique on TV and Sheldon's aloofness combined with Amy's desire for romance makes for guaranteed laughs.

These changes aside, the show has been able to maintain the core things which make it unique. The Big Bang Theory is still filled with references to Star Trek, Star Wars, and countless other movies, comic books, and TV shows. Despite the fact that it's one of the most popular shows on TV today (new episodes and in syndication), the show never shies away from trotting out geek pop culture or dense scientific jargon. Apparently they know that they've captured their audience and that things like that won't scare them off. In fact, some of the nerd stuff reaches new heights in Season Six. Apparently, someone at D&D headquarters called the show and either complained or made a great offer, as the guys play Dungeons & Dragons on not one, but two episodes (the second of which is a classic).

Changes in direction or geekiness aside, the bottom line is that The Big Bang Theory continues to be one of the funniest shows on TV, and the origin of the much of that comedy remains the unique Sheldon Cooper. Jim Parsons is racking up the Emmy Awards for this role, and he certainly deserves them as Sheldon often has the funniest moments on the show. There was a period where the writers were allowing Sheldon's disdain for others to come off as cruel, but they've backed off on this, and he's actually becoming more human. This doesn't stop him from harshly judging others and creating laughs. The Big Bang Theory is that rare show which can be very silly at times, but it remains clever and never talks down to its audience.

The Big Bang Theory: The Complete Sixth Season reinforces Sheldon's dislike of "hippies" on Blu-ray Disc courtesy of Warner Home Video. The 2-Disc set (which also includes the episodes on 3 DVDs) contains all 24 episodes from the show's sixth season. The show has been letterboxed at 1.78:1 and the Disc contains an AVC 1080p HD transfer which runs at an average of 15 Mbps. The image is sharp and clear, showing no noticeable grain and no defects from the source materials. The colors look very good, and the image is never overly dark or bright. The level of detail is good and we get nice depth in some shots, as the actors are separate from the backgrounds. The Disc carries a DTS-HD Master Audio 5.1 track which runs at 48 kHz and an average of 2.1 Mbps. The track provides clear dialogue and sound effects. For the most part, this is a standard sitcom track, with the dialogue coming from the center channel and a handful of stereo effects. The laughter of the live audience typically comes from the rear speakers. The unique thing about The Big Bang Theory is that the "atom shot" which signals a scene change offers notable subwoofer effects.

The Big Bang Theory: The Complete Sixth Season Blu-ray Disc contains a few extras. Disc 1 kicks off with "The Big Bang Theory: The Final Comedy Frontier" (11 minutes) offers comments from real-life astronauts Mike Massimino and Buzz Aldrin who talk about Howard's trip to space. The cast Skypes with astronaut Joe Acaba, who is aboard the International Space Station, in "Houston, We have a Sit-Com" (10 minutes). "The Big Bang Theory at Paley Fest 2013" (28 minutes) offers a panel discussion with the cast and the show's producers fielding questions about the show and the characters. Disc 2 opens with "Electromagnetism: The Best Relationship Moments in Season 6" is broken down into four sections -- Leonard & Penny (8 minutes), Sheldon & Amy (10 minutes), Howard & Bernadette (6 minutes), and Raj (7 minutes) -- where the actors talk about how romance effected their characters in the sixth season. (It's interesting to hear Rauch's real voice.) The final extra is a 9-minute GAG REEL.