Card of the week is a brief event happening before every episode in the Yu-Gi-Oh! 5D's Dark Signers arc (not shown in the dub). There are 5 cards, and after the 5 are shown, the middle card is picked by Leo and Luna, and they will briefly talk about it. The middle card is always the featured card of the episode.
Before the 5 cards turn over to be shown, the twins say "What could it be? What could it be? This is what we have this week!"