Both `iy-go-to-char` and `zap-up-to-char` take a prefix argument and a character argument prompted for in the minibuffer. Both functions seems to implement this by using `(interactive "p\ncPrompt string: ")`. But they behave very differently in `multiple-cursors-mode`: `iy-go-to-char` only prompts once for the character and uses that same one for every cursor; `zap-up-to-char` prompts for a character for each cursor.

I'd like to know why multiple-cursors treats them differently, but above all I'd like to have them both behave as `iy-go-to-char` does: single prompt, reuse that character for all cursors.