Many scenes or parts of scenes are cut from the episodes for syndication, to make room for the much larger number of commercials present today.
The famous opening credit sequence, where the names appear over a heart, was not a part of the original series run. Originally, various cartoons related to the show and the show's sponsor were used. The version everyone knows today was created for syndication. TV Land "restored" the original opening for its broadcasts. However, the references to the sponsor were replaced with a TV Land logo; as such these openings have only been seen on telecasts on said network, and by the early-2010s, TV Land started reinstating the "heart" credits on its reruns.
Many references to the sponsor, Philip Morris, were cut from the original negatives of episodes circa 1956. The DVD releases attempt to restore as many of these as possible using whatever source material exists.
In reruns of the series, much of the music in the beginning and end of scenes were altered or cut to make way for more commercials. Where possible, many of these musical bridges and cues have been fully restored for the DVD release.