Game & Wario wasn't always meant to be a standalone game. The upcoming Wii U game was originally planned to be a small demo pre-installed on Nintendo's latest console. However, Nintendo's Goro Abe explained that trying to make an experience that would appeal to everyone ended up being too restrictive for the creative process, and led to the game spinning off into a full release.
"The original plan was that the game would come pre-installed on the Wii U console, so it wasn't actually conceived of as being part of the WarioWare series," Abe told Nintendo president Satoru Iwata in a new column. "We began working on something that we could present and which would be easy for people to pick up and play."
He explained that because these mini-games would come built into the console, "we didn't want something that would only appeal to a certain section of customers." However, it conflicted with the WarioWare team's goals. "The WarioWare team have always had free reign to come up with all kinds of zany ideas, but we now found that we had to restrain ourselves... we would put to one side all those crazy, out-there ideas that might have really appealed to certain players, but not to everyone."
But apparently, after playing the game, Nintendo's Yoshio Sakamoto told the team to "shake things up," and perhaps not take things so seriously. With the creative restrictions lifted, the team ended up coming up with "too many ideas for a game that was going to be pre-installed," Abe explained.
And so, Game & Wario was born, transformed into a full retail release. You can see the fruits of their labor in June when the game releases on Wii U.