Goofs

When Wayne and George are talking and George is bent over, only one button on his three button shirt is buttoned. When he rises after being asked about Sheldon's "hernia", two buttons are seen buttoned.

When Wayne hands George the forged note, George takes it and holds it by its right side. When the camera angle changes to face Wayne, George is seen holding the note by its left side. The camera angle changes back to face George, he's holding it again by its right side.

While discussing Star Trek (1966)'s Captain James Kirk with his grandmother, Sheldon mentions the Kobayashi Maru test. This was not part of the Star Trek mythos until Star Trek II: The Wrath of Khan (1982) premiered in 1982. However, as the series is set seven years later, in 1989, it's completely conceivable that Sheldon has seen the movie and is well-versed in what continuity it established within the "Star Trek" canon, including Kirk cheating in the Kobayashi Maru.

The family dinner is spaghetti with meatballs, but Sheldon of the modern era has repeatedly commented that his mother made spaghetti with cut up hot dogs.

Missy, who is way more cynical than Sheldon, should have noticed that there was no dirt on the coins or shovel that Sheldon was using to trick her. Nor that Sheldon would voluntarily go outdoors to dig in the ground for any reason.