What is the first TV show to have reruns?
Answer I Love Lucy was the first show to be re-broadcast as a rerun. Desi Arnaz (Ricky Ricardo character in show) insisted that the show be filmed before the thought of syndication had ever come about.
I Love Lucy was the first sitcom to be filmed in front of live audience. It was not the first series to be filmed. Jackie Gleason's The Life of Riley was filmed in the 1949-50 season. Amos 'n' Andy was filmed and broadcast more than three months before I Love Lucy. Reruns of either could have been broadcast before I Love Lucy aired its first rerun. If "reruns in syndication" was meant then Amos 'n' Andy may have been the first since it was seen first run in syndication in the 1953-55 seasons and may have shown reruns long before I Love Lucy went into syndication in the 1960s. There may have been dramatic series filmed and rerun before I Love Lucy. Real answers aren't always so simple.
Depending if you mean what is the longest running show that has been in reruns? or what is the longest running show that airs reruns? I Love Lucy aired from 1951 to 1957 & is still in syndication. As far as I can find, the longest currently running show [as of January 2018] that airs reruns is Sesame Street which debuted in 1969.
youtube No - actually I think the question is asking for a source of full episode reruns, just as if the show was TiVo'd. Youtube has video clips. I've also looked for a long time for a legitimate website for reruns. Because the show is syndicated, it appears that full episode reruns are not available to stream online.