There is a really EASY yet cheap method of doing this. You can die. Your brother can die. Dead easy.
Play the level as normal. Doesn't matter if you die, or if Felix dies. Just keep going.
Play all the way to the end of the level. In the final room (two vines, two pistons and a breakable door), hit start and return to main menu.
Now when the game reloads, it starts a fresh death counter, just finish the last puzzle and the game will think neither you or Felix have died.