That's monkey business! "You are a cheeky monkey!" or "Real brass monkey weather!". Can also be used in a playful way, while fooling around or referring to the animal itself.
The monkey face emoji was introduced in 2010 and released as part of the Unicode 11.0 standard. This emoji can be found under the animals and nature
category. Because the monkey face emoji has been around for quite some time, it should display correctly in the majority of operating systems.