The old alternating-lines take was alive and well at many studios in the 1930s—Carlo Vinci used the same effect in the late ‘50s at Hanna-Barbera—and it found a home in Beverly Hills at the cartoon plant of Ub Iwerks.
Here are a couple of examples from Nurse Maid (1932). The old crone mother realises her baby (and his paid sitter, Flip) are missing. One of the two drawings has wavy lines of the character. They’re alternated for a shaking effect.
A cop peers around the corner. Then comes an eye-popping, surprise take featuring the radiating lines they loved so much at the Iwerks operation. (A slapdash background drawing, isn’t it?)
No animators get screen credit in this cartoon.