探头探脑 Origin — Chinese Character Wiki

tàntóutànnǎo

to stick one's head out and look around

探头探頭 tàntóu

to pop one's head out

To stretch or stick one's head out (to look around or peer into a space)
探 tàn verb

to stretch forward

to stretch or pop forward; to crane one's neck or lean out
脑腦 nǎo nounlocative

head

(bound form) The head; often used in phrases describing head movements or appearances.