When Alvin loses his red cap at a concert, he vows not to ever sing again. Determined to find a new cap before their sold-out concert, The Chipmunks go to the Hat Shack. When Dave buys him a new one, Alvin realizes that someone probably took his hat as a souvenir so he sets up a hotline offering an award. They are alerted to some possible sightings of the hat, but these leads turn up empty. Just as it's time to begin their big concert, Simon spots a janitor using the hat as a dustpan.
- "The Heart of Rock & Roll" originally performed by Huey Lewis and The News.
- The title of the episode refers to the phrase, "Here today, gone tomorrow."
- Some of the performance frames are used in the series' theme song.