"Pilot": While inviting Penny to lunch Leonard mentioned that they had curry which is a natural laxative. Sheldon said that during lunch invitations one should avoid references to bowel movements.
"The Cooper-Hofstadter Polarization": Sheldon told Penny he couldn't poop this morning due to the way he is affected by conflict with Leonard.
"The Pork Chop Indeterminacy": Sheldon tells his sister she can tell his mom that he's healthy and has been having regular bowel movements.
"The Financial Permeability": Sheldon says he can't wait until after the movie to eat dinner because it will delay the next morning's bowel movement until after he has to go to work.
"The Monopolar Expedition": Sheldon said he wakes up at 8:00 and moves his bowels at 8:20.
"The Pirate Solution": Raj tells Sheldon that odor won't bother him because he comes from India where cows roam the street and nobody has had a solid bowel movement.
"The Creepy Candy Coating Corollary": Bernadette said her mom calls her at work to make sure she had a healthy lunch then Howard said his mom calls him at work to make sure he had a healthy bowel movement.
"The Staircase Implementation": Sheldon asked what time Leonard evacuates his bowels.
"The Shiny Trinket Maneuver": Sheldon explained he was annoyed because he stepped into the bathroom to move his bowels and by the time he left the bathroom Howard dominated the apartment with his magic act.
"The Werewolf Transformation": Sheldon felt his life was falling out of order because his barber couldn't cut his hair and felt his other routines might be pointless, including his bowel movement chart from the refrigerator. Leonard is relieved to have that disgusting chart removed.
"The Zarnecki Incursion": When Penny and Priya were having a conflict, Amy mentioned that humans have a primate instinct to throw their feces at each other.
"The Flaming Spittoon Acquisition": Sheldon was saying things in his life were going well, which included him saying that his bowel movements are as regular as a German train schedule.
"The Spoiler Alert Segmentation": Sheldon was repeating statements Leonard said to him which he found annoying, including "Sheldon, don't talk about your bowel movements over breakfast."
"The Workplace Proximity": Sheldon says he took the expression, "Don't eat where one defecates" literally which is why he had not used a bathroom at a restaurant.
"The Relationship Diremption": On a double date between Bernadette/Howard and Emily/Raj, Emily recognizes Howard as someone she planned a date with in the past. When Howard arrived at Emily's place he needed to use the bathroom. The toilet was clogged which resulted in a large mess in the bathroom. Howard was too embarrassed to go on the date so he left through the window so he would not have to face Emily. Howard was nicknamed "Clogzilla" because of this.
"The Commitment Determination": During an argument, Mary Cooper told Beverly Hofstadter that she (Mary) studies Jesus Christ who teaches love and compassion while Beverly studies Sigmund Freud who teaches us why we hold in poop.