It's a shame these fasteners found their way onto lawnmower wheels. It is a sure sign of engineering intention - to produce throw-away goods.
I used to see them on toys and washing trolleys. Some clips were quite nice, with a built-in chrome hubcap.
They go under many names - some proprietary, some generic. Generally speed nuts will retain a hex shape (easy for removal). Speed clips and star locks are easy to install (as Tyler describes), but are buggers to get off.
It's almost a surgical procedure. There is no shortage of removal ideas:-
Rytool makes a good 4-piece pick and hook set of clips ...
