The character of Sheldon Cooper was inspired by a computer programmer personally known to series co-creator Bill Prady. He is named in honor of actor/producer Sheldon Leonard and Nobel Prize Laureate Leon Cooper.
The infection is caused by bacteria. However, excessive use may irritate you. Soda also dehydrates you, and for proper urinary health you should be drinking lots of water, and also cranberry juice. Your physician was definitely right in telling you that it could have made the bladder infection worse.
I drink diet soda every day. Drinking a reasonable amount of diet soda a day, such as a can or two, isn't likely to hurt you. The artificial sweeteners and other chemicals currently used in diet soda are safe for most people, and there's no credible evidence that these ingredients cause cancer.