YMMV / Karaoke Revolution

• Growing the Beard: The original Karaoke Revolution had very basic features compared to the later games. Vol. 2 would introduce the Quickplay mode, and Vol 3. introduced Duets with Lead and Harmony vocals. By Party, it seemed that Harmonix finally got the hang of it, with a new score system, more animations, and a much bigger setlist.
• Scrappy Mechanic: Party introduced a lot of new mechanics, which were all great, except for the Sing and Dance mode. This requires a player to stay on pitch with the song while they're on a DDR pad following the arrows. If this sounds confusing to follow, it's because it is. The mode was dropped afterwards in later games.
• Spiritual Successor: Vocals in Rock Band borrow heavily from the mechanics of Karaoke Revolution, integrating the Guitar Hero scoring system and Star Power (re-named "Overdrive") into it. Later versions went further by adding three-part harmonies (The Beatles: Rock Band and Rock Band 3) and improvisation features (Rock Band 4).
• Unintentional Uncanny Valley: The 2009 game falls under this. Blitz Games was trying to go for realistic looking graphics as part of the reboot and well....they come off looking really bizarre. Even worse at some of the options for creating characters. The 360/PS3 versions of the American Idol games to this extent as well, which have Simon, Randy, and Paula looking very robotic in their movement and extremely shiny.