Neither one knows how to whistle!
Edward Snowed-in
You just put your lips together and whistle
There was a face off at centre ice.
So they won't whistle on the way down.
Chimney Cricket!
To prevent them from whistling.
So they don't whistle on the way down.
Because dogs can't whistle. (X-post from r/dadjokes)
Because they can't whistle!