As a kid we would go out in the car, often to someone touristy and then beep and wave to a tourist family.
If someone lets me out at a junction I may blow them a kiss instead of waving.
I occasionally give presents to the bin men, they get the left over Halloween sweets or (non alcoholic) beer when its hot. Not exactly silly but they do a good job.
When my carer came in I once asked him to check the bathroom for a leak.
He came back out and threatened to beat me to death with the leek he found.
One Easter the local pub had loads of toy rabbits out as decorations, by the time we left a few were in compromising positions doing what rabbits do.
I looked after my friend's cat for a week, I sent my friend a text update, this developed into the cat being a secret agent and my friend sending instructions ot 'agent cat's name'.
The same friend we once went with her husband to their friends house. You could see the house phone in the hall through the glass door so we phoned the house number, as he was about to ick up we rang off and called his mobile, when he went to get his mobile we knocked on his door and ran off, when he opened the door we rang his landline I think this went of for 15 mins and we couldn't stand for laughing.
I turn the toilet roll round in people's houses.
My carer and I invented the 'Kitty Olympics' where we state what the event will be such as, 'doing the uppy downy walk on fences', best sleeping position etc.
My old cat charlie was very vocal and would 'talk' I used to have full on conversations where I'd say, "Dis you really, what happened then" and he would make a noise and then I'd ask another question.
Since my brother got married we have always lived hundreds of miles apart. Being the doting aunty I have bought my nieces and nephew lots of noisy toys.