Fermions are well known for NOT being able to exist in the same state, whereas bosons can. Hence why once an S orbital in an atom has two electrons (with opposite spins), that's it. But I've only ever seen this discussed for a single type of particle at a time. For instance, could a muon and an electron exist in the same state? Now, I realize this is a bit hand-wavy, since the orbital energies of a muon would (I suppose) be different than an electron... but imagine they weren't. Would there be any restriction to a muon and electron in an atom sharing all 4 quantum numbers? This would mean that so long as you had a bunch of different types of fermions (muons, taus...) they could 'overlap' like bosons. This seems strange to me. Or am I missing something? Thanks!