Most often, continuity has to do with the grille which is a major element of the face a car presents to the world: think Rolls-Royce, Mercedes, BMW and others. Sometimes other parts of a car are given styling continuity. In recent years BMW has used the shape of rear side windows in this manner.
An earlier instance is the Pontiac "Silver Streak" brand-establishment motif used for model years 1935-1956, inclusive. A short history is here, and I might write about how the streaks varied over time in a later post.
One factor in General Motors' success during the period 1925-65 was that a hierarchy of brands was established. For most of that time it was Chevrolet, Pontiac, Oldsmobile, Buick and Cadillac in that order from entry to luxury. The concept was that a young adult buyer might start with a Chevrolet or Pontiac, then had a path within the GM lineup to buy more expensive cars as his income grew over time. On the other hand, Ford offered nothing but inexpensive Fords and luxury Lincolns for most of the 1920s and 30s.
Silver Streaks gave the Pontiac line a measure of distinction during the many years when the brand was little more than a placeholder between Chevrolet and GM's more upscale marques. Besides the Streaks, Pontiac also had eight-cylinder motors offered on some of its models whereas Chevrolet only had sixes.
The Silver Streak motif usually consisted of a set of parallel chromed ribs running along the hood from front to rear and a similar set running down the center of the trunk. The initial 1935 version had the streaks cascading down over the grille with no streaks at all at the rear of the car. This ornamentation recognition device proved highly successful, which was why it was retained for so many years.
For 1935, General Motors introduced new, all-steel bodies (with no canvas inserts on their tops) for Oldsmobiles, Pontiacs and Master series Chevrolets. As the images above indicate, the cars looked pretty similar, especially when viewed from the side.
Viewed from the front, those Silver Streaks made a huge difference. Pontiacs became truly distinctive, never to be mistaken for a 1935 Chevy or Olds.
This shows Pontiacs from more normal viewing angles. Again, the Silver Streaks stand out.