The title refers to the fact that this is the 300th episode of Dallas (1978). Larry Hagman (J.R. Ewing) and Linda Gray (Sue Ellen Ewing) are the only actors to appear in all of the first 300 episodes.
This is the first episode in which Ken Kercheval (Cliff Barnes) does not appear since The Search (1982). His absence from this episode ended a streak of 208 consecutive episodes which lasted from Denial (1982) to The Serpent's Tooth (1989). The only actors to appear in more consecutive episodes are Larry Hagman (J.R. Ewing) at all 357, Linda Gray (Sue Ellen Ewing) at 307 and Victoria Principal (Pamela Ewing Barnes) at 210.
This is the first episode in which neither Victoria Principal (Pamela Ewing Barnes) nor Ken Kercheval (Cliff Barnes) appear. As such, this is the first episode not to feature a member of the Barnes family.