The Big Bang Theory came into itself when it began to focus on the strangeness of its central characters, and their disconnect from normal, everyday human life. As a result, there is often a low-level weirdness to most episodes, with one or more of the gang's members acting in an unusual way and the episode telling of the resulting hijinks.
Nonetheless, even with such an unusual base, there are some episodes that stand out head-and-shoulders above the rest in terms of strangeness. Whether due to outlandish plots, unusual character choices, or simply amplifying the characters' usual oddities tenfold, some The Big Bang Theory episodes reverberate weirdness from start to finish.
9 "The Transporter Malfunction" Has A Talking Spock Doll
When Penny surprises Leonard and Sheldon with a pair of vintage Star Trek toy sets, including the show's famous transporter and a doll of Mr. Spock, the two initially plan to keep the boxes closed and the toys in mint condition, as they do with many of their nerdy possessions.
However, the episode's main plot consists of Sheldon's Spock toy, voiced by Leonard Nimoy himself, speaking to Sheldon and guilt-tripping him into opening the toy, before continuing to influence him after the toy breaks. The strangeness is toned down because the conversations only happen in dreams, but it's a hair stranger than the show's norm.
8 The Gang Finds A Priceless Movie Prop in "The Precious Fragmentation"
Over the course of the show, much is made of the gang's love of movies and movie props, but one of the strangest episodes surrounding this phenomenon is "The Precious Fragmentation." A random box of junk turns up, containing a supposed lost prop version of The One Ring from Lord of the Rings, which is worth thousands.
Even without the sheer unlikelihood of this ring being found in a box they paid $60 for, the gang members all act irrationally over the ring, each with a different idea of what they should do with it. The strangeness only continues as they engage in a 'holding contest,' where they refuse to let go of the ring, even for climbing stairs or using the bathroom.
7 "The Werewolf Transformation" Shows Sheldon Abandoning All Rules
One of the most notable character traits of Sheldon Cooper is his rigid adherence to rules and systems, whether they exist in an institutional setting, as part of his taught Southern courtesy, or simply in his own head. When his barber's injury causes him to miss a rigidly-scheduled haircut, Sheldon abandons the systems in his life all at once.
Spurning his spot, normal bedtimes, and even his precious roommate agreement, Sheldon's antics in this episode lead to a stranger atmosphere than normal, with the strangest part being a musical stand-off with Leonard while he plays bongos in the early hours of the morning.
6 "The Cruciferous Vegetable Amplification" Introduces A Robotic Sheldon
Sheldon Cooper is obviously the strangest of the four 'nerd' scientists in the show, despite them all having quirks and neuroses, and so his 'regular' strange behavior is often the go-to for the writers to make an episode stranger than normal.
In "The Cruciferous Vegetable Amplification," Sheldon's increasing fear for his life leads him to confine himself to his room, and instead construct a rudimentary robot, including a television to project his face and let him converse. It's a strange concept for an episode, but one that leads to hilarity, especially when Steve Wozniak gets involved.
5 "The Thespian Catalyst" Includes A Bollywood Dance Number
Raj's unresolved feelings for Bernadette, Howard's girlfriend and later wife, are a recurring plot point early in The Big Bang Theory's run, with him at several points wanting their relationship to fail despite his friendship with Howard.
The episode in which this is most explicit is in "The Thespian Catalyst," where Raj fantasizes about a series of episodes where Howard lets him sleep with Bernadette. Already strange fare for the show, the ante is upped when Raj hallucinates a Bollywood-esque dance number involving him and Bernadette.
4 "The Nerdvana Annihilation" Features Multiple Imagined Spots Around A Lifesize Time Machine
Another case of the 'gang gets their hands on a movie prop' episode, in "The Nerdvana Annihilation," Leonard impulse-bids on what he believes to be a miniature of the time machine prop from The Time Machine, only for it to turn out to be lifesized, and for Leonard to need to split it four ways with the others to afford it.
Already a strange premise, the episode then has lengthy imagined sequences where both Leonard and Sheldon imagine actually using the prop to travel through time, in Leonard's case using it to impress Penny, and in Sheldon's case traveling to the future and being attacked by mutants.
3 "The Helium Insufficiency" Has Leonard & Sheldon Watch Movies With A Criminal
A plot point the show has used more than once is the gang considering committing petty criminal acts, usually at the instigation of Howard, with their neurotic dithering causing much of the action of the episode. The most severe case of this comes when Leonard and Sheldon cannot obtain helium in order to carry out an experiment testing their theory, with a ticking clock.
In a significant step up from stolen Comic-Con passes, they attempt to buy helium, a controlled substance, from one of Howard's contacts. They ultimately end up doing so, despite how out-of-character this is for them, and the possibility of federal prison. But in a weirder turn, after some intellectual sparring with the dealer, they end the episode watching Ernest Goes to Jail with him.
2 "The Proton Transmogrification" Has A Killed-Off Character Appear As A Jedi
Bob Newhart made several guest appearances as Professor Proton on The Big Bang Theory, a Bill Nye-type figure who is idolized by Sheldon. For an episode commemorating Star Wars Day, the show decides to kill off Professor Proton, and have Sheldon's plotline focus on grieving him instead of watching the films.
Throughout the episode, Professor Proton appears to Sheldon in a send-up of Obi-Wan's scenes as a Force Ghost, helping Sheldon resolve his feelings about his idol's death. Despite some emotional moments, it is a highly strange episode.
1 "The Spoiler Alert Segmentation" Has Mrs. Wolowitz Imprison Raj
Debbie Wolotwitz, Howard's mother, is a recurring character in the show, but is never seen, only heard through her loud voice, usually with humorous dialogue. Her personality points to her being controlling and somewhat amorous, but usually in a benign, benevolent way.
In "The Spoiler Alert Segmentation," Raj's subplot consists of him being kept prisoner in the Wolowitz household after he checks in on Howard's mother, when she begins to guilt-trip him with loneliness. What begins as Raj feeling obligated to stay turns into a mini-Misery situation, ending with Raj being dragged back in through a window during an escape attempt. It flies in the face of Mrs. Wolowitz's usual personality, and the events are never mentioned again.