A Suitcase Full of Cash and a Yellow Clown Car - S5-E16
Factual error: In the closing shot of this episode, a pile of cash is down close up. The bills are current circa 2000s and the show is set in the late eighties. The bills didn't have the current security markings that we have now.
White Trash, Holy Rollers and Punching People - S5-E21
Factual error: When Georgie goes to the doctors office with Mandy, when he walks in you can see a modern covid-19 safety poster behind his shoulder. (00:11:00)
Babies, Lies and a Resplendent Cannoli - S5-E18
Other mistake: Georgia tells candy he'll soon be 18, in March. That same day, Sheldon says Isaac Asimov died - which happened on April 6, 1992.
Answer: Mary is highly religious and completely against any form of alcohol as shown in Big Bang Theory numerous times.