There were no Fiji mermaids or dog-faced boys to be found at the “Cabinet of Wonders” show at the Brattle Theatre last Thursday, but the odd variety-show format ensured that its shelves were well-stocked with exotic curios. First, the night’s host — Hastings-born, Dylan-inspired singer-songwriter John Wesley Harding — tore into a few earwormy numbers off his new album, Who Was Changed and Who Was Dead (Rebel Group).