How to sing with a chipmunk voice

How to sing with a chipmunk voice
Back at the christmas challenge thread, I posted "Christmas don't be late" (Alvin and the chipmunks) where I sing with a chipmunk voice. @Furious_Phil requested that I made a video of how to sing like a chipmunk, so here it is
You don't need a pitch shifter or some other gear/effect, just basic knowledge of how to do it + the ability to sing in head voice (falsetto) to get that bright chipmunk sound.

Comments
Peace, Tony
I sing the verses in a baritone, low voice, and the turnarounds are a space alien, who speaks in a voice similar to the chipmunk sound. So I shift from super low to super high instantly.