The guys follow a strict schedule imposed by Sheldon. Sheldon's schedule often determines where the guys eat each day of the week and what activity they enjoy each evening.
Sheldon has oatmeal for breakfast, not French toast, as he explained in (The Gothowitz Deviation). Years later, Leonard makes breakfast for Sheldon (The Mystery Date Observation) and Penny wonders if he's worried about making French toast on Oatmeal day.
The guys have Thai takeout and Sheldon orders mee krob and chicken satay with extra peanut sauce (The Cooper-Nowitzki Theorem). Sometimes the guys have ordered from Szechuan Palace instead on Mondays (The Cushion Saturation).
The guys eat at the Cheesecake Factory. Sheldon orders a barbecue bacon cheeseburger; barbecue, bacon and cheese on the side. Tuesday used to be Big Boy night, but they switched in October 2007 (The Hamburger Postulate).
Thursday night was at one time Souplantation night, but Sheldon changed this to Big Boy night when they started eating at the Cheesecake Factory (The Hamburger Postulate). This later changed to pizza night, where Sheldon orders one with sausage, mushrooms and light olives (The Cooper-Nowitzki Theorem). The guys decided to make the third Thursday of every month "Anything Can Happen Thursday" in (The Hofstadter Isotope), which was later revived in (The Anything Can Happen Recurrence).
Friday night is Chinese takeaway and Vintage Game Night (The Codpiece Topology).
Sheldon gets up early to watch Doctor Who on BBC America (The Dumpling Paradox). He eats a bowl of Shredded Wheat with a 1/4 cup of 2% milk. Saturday night is also Sheldon's laundry night (The Panty Pinata Polarization) at 8:15.
Some of the guy's activities, such as Wii Bowling Night and Rock Band Night, do not appear to be as regimented.
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Sheldon decides that Tuesday nights will no longer be Big Boy night and instead they will eat at the Cheesecake Factory. As a result, Sheldon decides Thursdays should be Big Boy night, knocking Souplantation off the schedule.
Sheldon reveals that Wednesday nights are Halo night.
When Penny sleeps on their couch Friday night, Sheldon is annoyed when he wakes up early Saturday to watch Doctor Who on BBC America with a bowl of Shredded Wheat as Penny is in his way.
Sheldon tells Ramona Nowitzki that on Monday nights he eats Thai food. Mee krob and chicken satay with extra peanut sauce from Siam Palace.
He tells another grad student, Kathy O'Brien, that on Thursdays he eats pizza from Giacomo's. He orders one with sausage, mushroom and light olives.
As part of Penny and Sheldon's tit for tat battle, Penny interrupts Sheldon's regularly scheduled laundry night: Saturday at 8:15pm.
Leonard tells Sheldon the cashew chicken he gets him on Monday nights isn't from Szechuan Palace, which closed down two years earlier, but Golden Dragon. Sheldon previously mentioned Monday night's are Thai food from Siam Palace, though it's not clear if they alternate.
The guys have the idea of making the third Thursday in every month "Anything Can Happen Thursday", where they break free of their usual (often Sheldon-imposed) schedule.
When Sheldon suggests they go to the comic book store on "Anything Can Happen Thursday", the guys complain they went to the comic book store the night before. Sheldon points out that Wednesday is comic book night, but going on Thursday night would be different as it's Anything Can Happen Thursday.
When Penny makes French Toast on a Monday, Sheldon tells her Monday is Oatmeal day.
In a bid to cheer up Sheldon, who's still coming to terms with his break-up from Amy, Leonard makes Sheldon breakfast. Penny asks Leonard if he's worried about making French toast on oatmeal day, suggesting the conversation was taking place on a Monday morning. Leonard points out he's also prepared oatmeal for Sheldon. When Sheldon gets up, Leonard tells him about the French toast and oatmeal, but Sheldon thinks that's a lot of carbohydratess for a man on the prowl again.