Despite being a perceived ratings failure by the network, it gave many viewers a glimpse at several already popular anime series from Japan for the very first time. Two of the series that aired during Giant Robot Week, Evangelion and Gigantor, became a part of Cartoon Network's Adult Swim programming schedule in 2005.
(schedule source: http://anime-tourist.com/article.php?sid=374&mode=thread&order=0&thold=0)
Several episode fragments from Gigantor were aired during the commercial breaks and in between episodes.
On the last day of Giant Robot Week, the Cartoon Network original short Lowbrow aired as a four-part "micro series" at half-hour intervals during the remainder of the Toonami block outside of the hourlong special event. This six-minute short was later expanded into the first episode of the wildly successful Megas XLR.
On the evening of the final day of Giant Robot Week, The Iron Giant aired on the Cartoon Network, followed by an episode of Dexter's Laboratory involving giant robots as a time filler. Although it wasn't marked as Giant Robot Week, Cartoon Network promoted the airing as "a conclusion to Giant Robot Week."
Neon Genesis Evangelion has long been controversial on several points, and so it was generally conceded that it would probably never air on American television at all. Given the show's graphic violence, sexual innuendo, and religious themes, fans were shocked when it was first announced that it would air on the Cartoon Network, especially during the daylight hours (then normally reserved for Toonami which has since been moved to Saturday evenings).
The show was heavily edited, mostly for blood, cigarettes, alcohol, nudity, and language (even words like "killed" and "berserker" were removed). But the surprising part was the complete removal of Pen-Pen, whose introduction was made during a scene that involved beer. The show was never intended to run in its entirety on Toonami but in 2005, the series returned to Cartoon Network as part of the network's Adult Swim block with much less editing for its entire run.
Another controversy spawned by Giant Robot Week was the lack of giant robot programming that was already on Toonami. Gundam, Transformers, and The Big O, all of which were featured on the official site, weren't seen at all during Giant Robot Week.
The X Bridge's Recap of Giant Robot Week:
The complete list of edits (compiled by Kyle Pope) can be found at these two links: