To clarify for those unwilling to follow the link to the site, the theorists' contention is that there were different performers hired through the years to portray the same "character" in the band. The theorists' research began with the "Fake Paul" theory from the early days of the internet, using photographic comparisons that appear to show individuals of different heights and with different features (esp. eyebrows and ears). This then extended to include all the members of the band.
What these theorists fail to take into account are the workings of perspective, the mechanics of camera lenses, and the natural effects of aging. Reading through some of their "proof" threads is like looking at SweatyYeti's Bigfoot posts in the GenSkep forum a few years ago: a bunch of colored lines and cheap image-editing software used by clueless ignorami.
It's fun for about five minutes, as one wonders how these people could fail to see the obvious explanations for the differences. Then it just becomes tiresome.