[novalysis]

It just occurred to me that Clannad might have inspired Little Busters, which in turn inspired Angel Beats.

Spoiler for Comparisons between all three Madea Works:

All three works deal with death, and shared artificial worlds.

In Clannad, Ushio, the daughter of Tomoya and Nagisa resides in the "Imaginary World". Arguably, the Imaginary World represents the dying dream of a single family. (If indeed, my interpretation is correct). Furthermore, it's implied that each route is a part of the same phenomena of the Imaginary world. Clannad reflects the regret of a family, of a single protagonist.

Little Busters takes the same concept, and instead expands it into the shared dying dream of a group of classmates and friends. Again, each route is just one iteration of the Dream World. In other words, Little Busters takes the same concept as the Clannad world, but now expands it into the common creation of all the Little Busters. Little Busters reflects the regrets of not just the protagonist, but every participant who created the dream.

Finally, Angel Beats brings this idea to it's logical conclusion, where an Afterlife "Dream World" gathers people from all across what is likely various times and possibly even universes, into a "School setting" that attempts to resolve regret. But rather than being an exclusive dream world, Angel Beats is Universalistic, taking in people with utterly no relations to one another, other than the regrets that binds them all. Angel Beats isn't just the Dream World of a single protagonist, or a group of friends. It is a dream world that is, with no clear source, gathering complete strangers together into a common dream. In Angel Beats, even a Suginiami (Riki's hopeless suitor) type character has the ability to come to the fore.

Furthermore, while the mechanics of the dream is utterly unknown in Clannad except to Ushio (perhaps), the mechanics of the Little Busters world is, while hidden, both knowable, and the participants have manipulated the dream far more obviously than in Clannad.

In Angel Beats, the mechanics are even less hidden. It is transparent, the surrealism of the world is more obvious. Furthermore, it is usable, and we can see the protagonist clearly knowingly exploiting the mechanics.

The hierarchy goes like this:

Clannad: The Dream of Family
Little Busters: The Dream of Friends
Angel Beats: The Dream of Strangers.

Clannad: Very hidden mechanics. (The Illusion cannot be known)
Little Busters: Mechanics kept secret. (The Illusion is knowable)
Angel Beats: Mechanics more blatant and easily known. (The Illusion is obvious)