A Wild Mouse roller coaster (also Mad Mouse or Crazy Mouse) is a type of roller coaster characterized by small cars that seat four people or fewer and ride on top of the track, taking tight, flat turns (without banking) at modest speeds, yet producing high lateral G-forces. The track work is characterized by many turns and bunny hops, the latter producing abrupt negative vertical G forces. When approaching a turn from a straight section, the intended impression is that one will simply continue straight, and thus plunge off of the device, this since there are no transition sections as are in a conventional high speed roller coaster track and the turn itself is obscured upon close approach. Almost all Wild Mice feature "switchback" sections, consisting of several of these unbanked turns, separated by straight sections. Usually the turns on the switchback section are 180°, but some coasters feature 90° turns as well as more rarely steep runs with loops (for example Crazy Mouse at Tobu Zoo in Japan, which is no longer operating). Some riders, usually among taller people, report sustaining whiplash after being subjected to these turns.The feeling of a Wild Mouse coaster is amplified by using cars that are wider than the track itself, giving the impression that the riders are hanging off the side or that they might fly out, thus giving it the name "wild".
Some may include trick-track — a "straight" piece of track banked slightly side to side designed to throw the rider left to right. Some wild mouse coasters, such as Primeval Whirl, also have spinning cars.
The modern Wild Mouse was invented by German designer Franz Mack. In the original wooden Wild Mouse coasters of the 1960s and 1970s, the cars were so small that they could only fit two adults in close contact. While the low capacity of these rides led to long lines, the cars were small by design.
Throughout the 1970s and 1980s, the Wild Mouse-type roller coaster was nearly extinct. However, beginning in the mid-1990s, Wild Mouse-style rides made a comeback for two reasons: first, they were cheaper than larger, conventional coasters; second, they added to a park's "coaster count" with minimal impact on cost and area.