Oh, for the days when variety shows dotted the schedule in much the same way "reality" shows do today. Shindig was one of those shows that routinely featured stars of other ABC shows of the period. Shindig! also spawned some imitations, one of which was the syndicated Shivaree, which lasted just 1 season. In the Shivaree clip presented here, The Addams Family's Ted Cassidy, appearing in character, of course, performed his novelty hit, "The Lurch", named for his character on the show.
The only other time that Cassidy did any actual "singing", if you can call it that, was when he performed the theme to the animated series, Atom Ant, which also premiered in 1965.
Now, let's see how many radio stations can, ah, dig this up on Halloween......!