When a sheep shifts its gaze up or down, its head stutters. This is noticeable at the standard tick rate, and even more so when the tick rate is turned down. As far as I can tell, no other mobs are affected.

To reproduce

1. /summon minecraft:sheep ~ ~ ~ {attributes:[{id:"minecraft:movement_speed",base:0d}]}

2. Fly a few blocks up from the sheep and wait for it to shift its gaze to and from you. Swapping to and from wheat will make this process faster.