Original sentence: Its basic premise was that of Sigmund (played by Billy Barty), a friendly (if somewhat cowardly) sea monster who runs away from his comically dysfunctional undersea family, and is discovered and befriended by two boys, Johnny (played by Johnny Whitaker), and Scott (Scott Kolden), who let Sigmund stay in their hideout
Edited sentence: Its basic premise was that of Sigmund (played by the immensely talented little person Billy Barty), a friendly (if somewhat cowardly) sea monster who runs away from his comically dysfunctional undersea family, and is discovered and befriended by two boys, Johnny (played by Johnny Whitaker), and Scott (Scott Kolden), who let Sigmund stay in their hideout