In Das große Tier-Rätsel, designer Gunter Baars has taken the picture-hiding and revelation device from Wolfgang Kramer's 1994 release Klappe auf! and built a new game around it. In that earlier game, one player would reveal sections of an image bit by bit until another player would guess what the image showed; the earlier you guess the image, the more points you score. For Das große Tier-Rätsel the core of that earlier game remains in place: Players try to guess the identities of animals hiding in the picture box. But in addition to that challenge, players need to guess various qualities about the animal in question: What does it eat? Is it faster or slower than a human? How many legs does it have? It is a mammal or reptile? Each animal card has two sets of questions relating to it, and players in the know will score additional points. The first player to circle the score track wins the game. Re-implements Klappe auf!