The 1980s "The Real Ghostbusters" cartoon show is almost as beloved as the classic film that spawned it, if not more so. The Emmy-nominated series ran for an impressive six years between 1985 and 1991, but never would've happened if not for this incredible pitch video.
Technically an unaired pilot for the show, producer/director Richard Raynis and animators Kevin Altieri and Eddie Fitzgerald created the clip to convince ABC that a "Ghostbusters" cartoon series would work. While a few bits were used in promotional materials and even the show's intro, the footage as a whole was never aired (though it was included on "The Real Ghostbusters: Complete Collection" DVD set).
Most interesting, however, are some of the design differences between the pitch and the eventual series. Right away, it's clear that the style has a bit more of an exaggerated anime-style feel to it. The character designs would also alter on their way to TV, as the ghost busting gear was closer to the movie versions and the GBs were originally shown in the tan jumpsuits from the first film, as opposed to the multi-colored outfits that were drawn later. Even their faces were different, with Peter Venkman especially looking more like his movie counterpart in Bill Murray. Slimer wasn't yet the comic sidekick and was still depicted as a menace, and the whole thing had a much darker palette and feel.
As Ecto-Web points out, a lot of these differences stem from the fact that the animators were working by the seat of their pants, with no outline or character models to work with except for the "Ghostbusters" film itself. The "Ghostbusters" Wikia has a pretty great rundown of all the differences, including side-by-side comparisons and closeups of the proton packs. Old-school fans can probably spot a lot of this themselves, of course, so watch the promo below.