Robotech
Three unrelated Japanese series cut together into one American saga, and the opening is where the seam shows: the same theme and the same establishing pan every week, then a different logo card and a different war.
Season 1
92sThe Macross Saga. A slow pan across a ruined landscape in a film-strip frame, then the SDF-1, the Veritech fighters and a pilot's helmet — all of it drawn from Super Dimension Fortress Macross, the first of the three shows folded into Robotech.
Season 2
91sThe Masters. Identical theme and identical opening pan, so the change announces itself in two places: the logo card gains a subtitle, and every frame after it is re-cut from Southern Cross footage.
Season 3
The New Generation. The third logo card, and Invid-era footage throughout — the last of the three source series, and the only one whose opening most American viewers met without ever knowing it had another name.