One memorable episode featured Boris Karloff, Lon Chaney Jr. and Peter Lorre. Karloff and Chaney were given the chance to don their famous Universal Frankenstein Monster and Wolf Man make-up for the first time in decades.
Although the series was called "Route 66" many of the episodes were set in areas in the United States which Route 66 did not travel through. For example, Route 66 begins in Chicago and ends in L.A., but two episodes were shot in New England, one in Maine (Year 4, episode 2, Same Picture, Different Frame) and one in Vermont (year 4, episode 3, Come Out, Come Out, Wherever you are) - both aired in the fall of 1963 and starred Martin Milner and Glenn Corbett.
George Maharis walked off the show during the fourth season during a bout with hepatitis, although the real reasons are known to be his dissatisfaction with his contract, as well as his ongoing clashes with co-star Martin Milner and the show's producers. He was replaced by Glenn Corbett, but audiences did not like the change and the show was canceled as a result.
Throughout the series there are numerous references to Tod having attended college at Yale, but did he graduate? In the last episode of Season 2 ({2-32} "From An Enchantress Fleeing") Tod mentions that he "ended his studies after his third year in 1960 and did not finish".
According to Glenn Corbett, none of the episodes he appeared in where shot along the real Route 66. When he asked the producers why, he was told that the scenery along the actual highway wasn't considered interesting enough.