If I have a {Meddling Mage} in play and the named card is {Thoughtseize}, my opponent played {Bloodbraid Elf}, cascading thoughtseize. Can it be played?
Nope, meddling Mage wins. Can't cast trumps cast for free, since casting for free is still casting. The thoughtseize is not legally castable and the cascade is essentially a failure, putting all of the revealed cards on the bottom (the thoughtseize included)