The flashbacks depict Karen as a college student in the late 1960s who is actively involved in the student protests of the era. However, she told David Crane in Let Me Count the Ways (1980) that she graduated from college in the early 1960s as part of "the last gasp of the Silent Generation" and therefore missed out on the student protests.
The flashbacks depict Karen and Sid as dating in the late 1960s. However, previous episodes indicated that they had already been married for several years by this time and would have already had Diana, Eric and possibly even Michael.
Gary sprained his arm in the preceding episode Say Uncle (1987). Although this episode begins immediately after the events of that episode, he is no longer wearing a sling and exhibits no signs of pain or discomfort.