Njengoba kunikezwe uhlu lwabadlali beBig Bang Theory, khetha abadlali abakhulu kuphela.
Context:UJohnny Galecki njengoLeonard Hofstadter: Usosayensi wokuhlola one-IQ engu-173, owathola iziqu zakhe zobudokotela lapho eneminyaka engu-24 ubudala. ULeonard uyisiphukuphuku esithanda imidlalo yama-video, izincwadi zamahlaya, ne-Dungeons & Dragons. ULeonard uyindoda eqondile yalolu chungechunge, ehlala efulethini ePasadena, eCalifornia, noSheldon Cooper. ULeonard uthandana nomakhelwane wakhe omusha uPenny lapho behlangana okokuqala, futhi bagcina sebeshadile.  UJim Parsons njengoSheldon Cooper: Odabuka eGalveston, eTexas, uSheldon wayeyingane eyisimangaliso enenkumbulo ye-eidetic owaqala ekolishi eneminyaka eyishumi nanye futhi wathola i-Ph.D. eneminyaka eyishumi nesithupha. Ungusosayensi wezifundo zemvelo ocwaninga ngemishini yama-quantum kanye nemfundiso-mbono yezintambo, futhi, naphezu kwe-IQ yakhe engu-187, ukuthola kunzima ukuqonda izici eziningi ezivamile zezimo zomphakathi. Uzimisele ukwenza izinto ngendlela yakhe, njalo uyaziqhayisa ngokuhlakanipha kwakhe, futhi unendlela yokuphila egxile kakhulu emikhutsheni. Naphezu kwalezi zinto, uqala ubuhlobo no-Amy Farrah Fowler, futhi bagcina sebeshadile.  UKaley Cuoco njengoPenny: Umlingisi othanda ukuvelela wase-Omaha, eNebraska. UPenny uthuthela ngaphesheya kwehholo lapho kuhlala khona uSheldon noLeonard. Usebenza ematafuleni futhi ngezinye izikhathi usebenza endaweni yokudlela eThe Cheesecake Factory. Ngemva kokulahla ithemba lokuba umlingisi ophumelelayo, uPenny uba ummeleli wokuthengisa wemithi. UPenny uba umngane kaBernadette no-Amy, futhi bavame ukuhlala ezindlini zomunye nomunye. UPenny noLeonard baba nobuhlobo futhi bagcina sebeshadile.  USimon Helberg njengoHoward Wolowitz: Unjiniyela wezindiza owathola iziqu zakhe ze-master eMassachusetts Institute of Technology. UHoward ungumJuda futhi wayehlala nonina, uDebbie (uCarol Ann Susi). Ngokungafani noSheldon, uLeonard, uRaj, uBernadette, no-Amy, uHoward akanayo iziqu zobudokotela. Uqeqeshelwa ukuba usomkhathi futhi uya emkhathini njengesazi sokuthwala impahla kuyi - International Space Station. Ekuqaleni uHoward wayezibheka njengendoda yabesifazane, kodwa kamuva waqala ukuthandana noBernadette, futhi bathembisana umshado bashada. UHoward uthambekele ekuchitheni imali ngamathoyizi futhi uxabana noBernadette ngenxa yengeniso yakhe ephansi ngokungajwayelekile njengonjiniyela kanye neholo lakhe eliphakeme njengososayensi bezemithi.  UKunal Nayyar njengoRajesh Koothrappali: Isazi sezinhlayiyana zezinkanyezi esivela eNew Delhi, eNdiya. Ekuqaleni, uRaj wayenenkinga yokungakhulumi, eyayimenza angakwazi ukukhuluma nabesifazane noma ukuba seduze nabo ngaphandle uma ephuze utshwala. URaj futhi unokunambitheka kwabesifazane kakhulu futhi uvame ukuthatha indima yowesifazane evamile ebunganeni bakhe noHoward kanye naseqenjini lamadoda amane. Kamuva uRaj uthandana noLucy (Kate Micucci), naye onenkinga yokukhathazeka emphakathini, kodwa ekugcineni kuphele. Kamuva ukhuluma noPenny ngaphandle kotshwala, enqoba ukungabi bikho kwakhe kokukhetha. Uqala ukuthandana no-Emily Sweeney, futhi kamuva ubuhlobo babo buba bodwa. Esikhathini sokugcina salolu chungechunge, uRaj unokuphinda futhi aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde aphinde. Unayo futhi i-Yorkshire Terrier okuthiwa iCinnamon. Laba badlali baqala ukufakwa njengosaziwayo bezivakashi futhi kamuva bathuthukiswa baba abadlali abakhulu:  USara Gilbert njengoLeslie Winkle (ophindaphindiwe isizini 1, obamba iqhaza isizini 2, isivakashi isizini 3, 9): Isazi sesayensi esisebenza elabhorethri efanayo noLeonard. Ngokubukeka, empeleni ungumlingani wesifazane kaLeonard futhi unemibono yesayensi ephikisanayo noSheldon. ULeslie walala noLeonard futhi kamuva noHoward. UGilbert wakhushulelwa esikhundleni sokuba yilungu eliyinhloko ngesikhathi sesizini yesibili kodwa wabuyela esimweni senkanyezi yezivakashi ngoba abakhiqizi abakwazanga ukuthola izinto ezanele zomlingiswa. UGilbert ubuyele kuThe Big Bang Theory esiqeshini sayo sama-200.  UMelissa Rauch njengoBernadette Rostenkowski-Wolowitz (isikhathi esiphindaphindwayo sesizini 3, edlala iziqephu 4<unk>12): Owesifazane osemusha ekuqaleni osebenza noPenny e-The Cheesecake Factory ukuze akhokhele esikoleni esiphakeme, lapho efunda khona i-microbiology. UBernadette wethulwa kuHoward nguPenny; ekuqaleni, abavumelani, ngokusobala abanalutho olufanayo. Bayaqomisana, kamuva bathembisane umshado futhi bashade. Nakuba ngokuvamile engumuntu omnene nonomoya omuhle, uBernadette uthukuthela ngokushesha futhi angaba nolaka futhi asheshe acasuke lapho ecasulwa.  Mayim Bialik njengo-Amy Farrah Fowler (inkanyezi yezivakashi isizini 3, edlala iziqephu 4<unk>12): Owesifazane okhethwe yisiza sokuphola online njengomlingani ophelele kaSheldon, u-Amy uvela eGlendale, CA. Ngenkathi yena noSheldon ekuqaleni behlanganyela ukungazi lutho kwezenhlalo, ngemuva kokwakha ubungane noPenny noBernadette, ekugcineni uba nentshisekelo enkulu ekuxhumaneni kwezenhlalo nezothando. Ubuhlobo bakhe noSheldon buqhubeka kancane kancane kuze kube yilapho uSheldon embheka njengentombi yakhe, futhi ekugcineni, bashada. U-Amy ukholelwa ukuthi yena noPenny bangabangane abakhulu, umuzwa uPenny angawuhlanganyeli ekuqaleni. U-Amy uneziqu zobudokotela kwezokwelapha.  UKevin Sussman njengoStuart Bloom (izinkathi eziphindaphindwayo 2<unk>5, 7, edlala izinkathi 6, 8<unk>12): Umnikazi wesitolo sezincwadi zamahlaya onomoya omnene, ongazethembi. Umdwebi onekhono, uStuart uthweswe iziqu e-Rhode Island School of Design ehlonishwayo. Nakuba enenkinga yokuzihlanganisa nabantu, unamakhono angcono okuzihlanganisa nabantu. UStuart usikisela ukuthi usebunzimeni bezimali nokuthi isitolo sezincwadi zamahlaya manje sekuyikhaya lakhe. Kamuva uyamenywa ukuba ajoyine iqembu lamadoda ngenkathi uHoward esesikhaleni. UStuart uthola umsebenzi omusha wokunakekela unina kaHoward kamuva. Ngemva kokufa kukaNkk. Wolowitz, uStuart uyaqhubeka ehlala emzini wakhe, kanye noHoward noBernadette, kuze kube yilapho ethola indawo yakhe.  ULaura Spencer njengo-Emily Sweeney (izinkathi eziphindaphindwayo 7<unk>8, 10, edlala isizini 9): Udokotela wesikhumba esibhedlela iHuntington. U-Emily waya eHarvard futhi uyakujabulela okubi, futhi uthi uyayithanda umsebenzi wakhe ngoba uyakwazi ukusika izinto ngemimese. Ngaphambi kokuba ahlangane noRaj, u-Emily wahlelwa ukuba ahlangane noHoward bengabonanga. Ngemva kokuthola iphrofayela ka-Emily yokuqomisana kuyi-Internet, uRaj ucela u-Amy ukuba amthinte njengomphelelisi wakhe. Ubudlelwano babo buba yi-exclusive, kodwa uRaj kamuva uhlukana no-Emily lapho ethandana noClaire (Alessandra Torresani), umphathi webha kanye nomlobi wezingane.
UKaley Cuoco njengoPenny, uMelissa Rauch njengoBernadette Rostenkowski-Wolowitz, uMayim Bialik njengo-Amy Farrah Fowler