I've known for a long time that who am i prints info about the current user. Today I learned it's synonymous with who -m, though not synonymous with whoami.

I also learned that the two words after the who can be any non-option arguments. The Linux man page says:

If ARG1 ARG2 given, -m presumed: 'am i' or 'mom likes' are usual.

For example:

$ who -m
alee     ttys019  Jan 28 21:58 

$ who am i
alee     ttys019  Jan 28 21:58 

$ who mom likes
alee     ttys019  Jan 28 21:58 

$ who fred wilma
alee     ttys019  Jan 28 21:58 

This works on the Mac too, even though the Mac's man page only mentions am i and not that you can use any two words.

So of course I've now added an alias whom so that I can type whom Mom likes. I actually pride myself on not being a grammar pedant. I make an exception in this case because it amuses me.