We introduce a strengthening of the notion of completeness for analytic quasi-orders called "invariant universality" (roughly speaking, an analytic quasi-order is invariantly universal if it contains in a "natural" way a copy of any other analytic quasi-order), and we then show that, quite surprisingly, many natural examples of complete analytic quasi-orders arising in various areas of mathematics are indeed invariantly universal.
This is joint work with Riccardo Camerlo and Alberto Marcone.