Good move and as you see αυτός can be used at the beginning or end...and for longer sentences in other places as well. We can't keep up with the alternative word order in Greek. :) But it makes for a very rich means of expression.
I first tried "Τι μιλάει;", but then I saw that "Τι λέει; is correct.
What's the difference between "μιλάω" and "λέω"?
Is it like Russian "говорить" and "сказать" meaning "to talk" resp. "to say"?
Does the Greek language have aspects as the Slavic languages do?
Which part? Greek does not use an auxiliary verb to form questions and the personal pronoun is commonly dropped, so no irregularities there. What = Τι and says = λέει, so it's all as regular as it can be!