1 They call your bluff.
At the park, when you threaten to leave (‘Come ON, it's time to go, I will go without you. BYE THEN’) they shoot you a look which says, 'You do that then' as they potter off back towards the slide. The little bastards. You then have to face the indignity of re-tracing your steps back through the gate and resorting to the Lift And Drag technique. All while parents of well-behaved children pretend not to look.
2 They overhear and repeat only the bad stuff.
Ask them to copy your recital of the alphabet, or numbers 1-10, and they become selectively deaf. But accidentally let the swear guard down due to some cockwomble's bad driving and be faced with ‘FUCK'S SAKE man’ clear as day for all to hear. Come on in, Social Services.
3 They lie down on the floor.
In public. Usually prompted by the earlier disagreement in the park, this little trick means they always have one up on you because they don't care what people think. They will go completely stiff and refuse to stand so you have to pick them up and carry them out of the Post Office by their coat hood. Later you will realise you forgot to post the letter.
4 They refuse to eat the food you give them.
You offer one last chance to start eating it properly before it goes in the bin.
They don't want it.
It goes in the bin.
They do want it.
*Scratches own eyes out*