"The Big Bang Theory" and "Young Sheldon" are set in the same universe, and both shows feature some of the same characters at different points in their lives. The main examples are Sheldon Cooper's (Jim Parson) family members, who are basically the heart of the entire franchise. Sadly, though, his dad, George Cooper Sr. (Lance Barber), is absent from the former series as he died when Sheldon was still in his teens. That said, Barber still has a role on "Big Bang Theory," and let's just say his character isn't as nice as George.

Unlike Barber's secret cameo in the "Young Sheldon" finale, his "Big Bang Theory" character is more out in the open. His name is Jimmy Speckerman, and "The Speckerman Recurrence" episode reveals that he bullied Leonard Hofstadter (Johnny Galecki) back in high school. When they meet again in the present, a drunken Jimmy apologizes for being...