What professions can be uncle & aunty-ized? Kids like to call grown-ups Uncle &amp; Aunty. Professions can even be uncle &amp; aunty-ized:

警察叔叔


  “一个人在家害怕,警察叔叔帮我找爸妈” 


In Sichuan there is even 护士娘娘


  护士娘娘,我嘴巴干的很,可不可以给我倒杯水啊!


What other professions can be uncle &amp; aunty-ized?
It is mostly for jobs that require wearing a uniform. The uniform provides a visual cue for children that these are special people who may be able to help them when needed. Note that 司机叔叔/司机阿姨 are for professional drivers, not any driver of a private car.