Another word of the day suggestion from a wonderful reader.
کلک / kalak / trick(ster)
Kalak can be a trick (good or bad) that you play on someone, but it can also be a term of affection as in ay kalak!, oh you little trickster! It's mostly used when talking to children (I use it a lot with my little nephew), but it can be used with adults too if you have a very close relationship with them. For example, if I made a surprise visit to see my parents, they would say "ay kalak! You told us you were coming next week!"
A synonym is حقه باز hoghebāz which can also be either good or bad and used affectionately depending on how you say it. When I was little, my uncle would often use both of them and say to me, "Chetori kalak? Hoghebāz!?", How are you, you little trickster?