I think it is nice if the puppeteer is in the curtain call too. Could the mouse come through the floor at the top of the treads. Depending on sight-lines and structure you could have a long narrow trap covered in overlapping lycra so he can arrive from the wings. The mouse takes his bow (all done by the ASM) and then the puppeteer comes from the wings, picks him up, while masking what he is doing with his body, and then joins the rest of the cast DS.