I really enjoyed Captain Toad: Treasure Tracker when I reviewed it last year; I thought it was a great little sleeper hit coming on the tail of Smash Bros. When the game was released Nintendo announced that it would have a free DLC minigame that made use of the Mario Party Toad Amiibo, and as of last week that DLC is live.
The cool people at Nintendolife have a brief video explaining how the mode works. Basically you scan the Toad Amiibo and he unlocks a fun little bonus game where you hunt for a pixelated Toad hiding in each level. I picked up a Toad Amiibo for Mario Party last week (contrary to fears and rumors, he wasn't rare at all in my experience) and I tried out the pixel Toad minigame.
It's like the Nintendolife people say; it's a goofy little bonus that doesn't add or remove a whole lot from the Captain Toad experience. I appreciate extras like this, but personally I think the Amiibo still need a game all to themselves to really show the full potential of the figurines. Of course, that would require Nintendo to supply enough of the figures to meet demand first...