Any song in the game can easily be "sung" to 100% by blowing steadily into the microphone on Easy difficulty. A fan should work for this, but if it doesn't seem to be working, simply exhale (inhaling works too) into the microphone during the singing parts.
Artie (in the wheelchair) is featured in two of the songs you must complete to 95% or better: "Never Going Back Again" is available from the song selection menu by default. In order to unlock "PYT", you must sing through 25 songs first. You will receive a message on-screen indicating that the song has been unlocked, after which you will be able to select it from the song selection screen.