The difference being that in these examples, the actors were intentionally appearing in the films. Next thing you know, they'll have the Powerpuff Girls listed in the credits for "A Mighty Wind"
http://www.imdb.com/board/10310281/
.
Still, if you watch the credits of "Madhouse"
http://www.imdb.com/board/10071790/
, you'll see names like Basil Rathbone and Boris Karloff, who are credited with "special contributions". These turn out to be film clips within the film, to help establish Vincent Price's character's cinematic past. Kind of exceptional. But you'll note that it mentions "archive footage" next to their names. In this case, I think the names are there because they are featured in the actual credits.

Yeah, that's fair enough.

It can still be included on the IMDB as uncredited.Stephen King has a cameo as a weatherman on the TV in the Storm of the Century and he is listed.

Yes, but those few seconds of flashback footage took up the whole screen.

Alan Rickman was credited in Die Hard: With A Vengence even though the only way he was in it was via flashback using footage from the first Die Hard movie.

That doesn't count. If an actor in a movie is watching a movie on the TV and another actor is in the movie showing on the TV, the actor on the TV does not get credit for being in that movie. For example, in the Cable Guy, Ben Stiller can be credited because he was playing a role in the movie. If Matthew Broderick's character had turned on Reality Bites or the Ben Stiller Show, Ben couldn't be credited as being in the movie. Using your logic, if Matthew Broderick had been watching the Godfather at some point in the Cable Guy, then Al Pacino should be credited as being in the movie. If anything, under "Movie Connections", the movie being watched on TV could be listed under "References". That's all.

Actually, you can submit that to IMDB to add to his credits if you register with them (no cost). Once you're registered, just click on "Update" at the bottom of that person's page. I remember the scene in "The Cable Guy", when Matthew Broderick was watching his infomercial. Funny stuff. Do you also remember similar scenes in "Beautician and the Beast" and "Men in Black"?

What character did he play in "The Cable Guy"?
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