It's what they're NOT airing.

Since 2000, Cartoon Network has been the exclusive cable home of perhaps the greatest mecha franchises ever created, Gundam. Toonami has seen several Gundam series premiere on the block, including Gundam Wing, Mobile Suit Gundam, 08th MS Team, Gundam 0080, and G-Gundam. Before that in 1997, Voltron: Defender of the Universe was a foundation which helped build this block we call Toonami. In 2001, The Big O, a new series that mixed classic mecha action with American sensiblities premiered on Toonami. Later in the year, two other mecha franchises premiered on two different mediums. Patlabor, the ultimate mecha police squad, premiered on Toonami Reactor (CN's premiere online episode outlet until it got replaced by Adult Swim Pipeline for a short period) while Zoids, based on a popular toy model kit, premiered on Toonami. While we're on the subject of Adult Swim, Pilot Candidate, a series that was edited to air on Toonami in the first place, premiered there in 2002 as did Gundam 0083. Oh, and Transformers Armada premiered in 2002 as well.

And despite all of this, none of those Toonami mecha franchises appeared during Giant Robot Week. At least on air. The Big O, the Liger Zero from Zoids, and Optimus Prime from Armada made a stop at the Giant Robot Week section on the official Toonami stop, and aside from the Advanced Robotics interstitial that's been airing more than usual on the block which heavily featured The Big O and Gundam, only the 4-5 PM hour has been the focus of the special week. And since the shows airing in that slot aren't normally seen on Toonami, it's safe to say that during Giant Robot Week, the giant robots of Toonami are being slighted.

A Toonami Giant Robot Week without Toonami-bred giant robots is like having a pizza without the pizza crust, a lot of topping, yet nothing to support it.