Years ago (early 90's) flying circuits on a calm day, on climbout I passed a helium filled 'Mr Blobby' balloon.
Each subsequent circuit I passed Mr Blobby in the same position - passing 500' AGL passing the left wingtip.
That was until I put out a radio call, whereby another local aircraft 'propped' it first go. Not bad considring that Mr Blobby was only about 2' tall, so you could only see him from close range.