When Lois and Clark are discussing if Leslie Luckaby could really be Lex Luthor Jr Lois said that Lex wasn't old enough to have a son Leslie's age. John Shea (Lex Luthor) is only 13 years older than Patrick Cassidy (Leslie Luckaby).
When Dr Klein was leaving to meet Carolyn, the girl he was interested in, he told Superman there was something he hadn't done in almost 5 years. That seems odd considering that up until the episode before he always wore a wedding ring.