Keeping your piano clean and free of dust, pet hair, and creepy crawlies is an important part of piano maintenance.
Most of the pianos I visit have not been properly cleaned in 10-30+ years. I have pulled just about everything out of a piano. French Fries, Dust, Bugs (both dead and alive!), Mice (mostly dead), and a host of Legos and other things that do not belong there. This is why I recommend a cleaning every couple of years – or – whenever your 3 year old announces they are missing their favorite toy.
NOTE: Due to the thousands of fragile moving parts inside the piano I do not recommend you attempt a Do-It-Yourself cleaning project.