Horgan has guest-starred with fellow Star Trek performers on many other television series, including: Daniel Boone with Paul Fix; Pistols 'n' Petticoats with Stanley Adams and Robert Pine; The Girl from U.N.C.L.E. with Arnold Moss and Sabrina Scharf; Twelve O'Clock High with Frank Overton, Bert Remsen, and Paul Sorenson; Mission: Impossible with Lee Bergere and John Crawford; Cimarron Strip with George Murdock, Ron Soble, and Grace Lee Whitney; and Bewitched with Elizabeth Rogers.