Wonder Momo (ワンダーモモ) is a beat 'em up arcade game that was released exclusively in Japan by Namco in 1987. It runs on Namco System 86 hardware, and was later ported to the PC-Engine in 1989. This game was never released outside of Japan, probably because of its slightly questionable content.
When the game is first started, players are treated to a parody of the MGM logo featuring Momo instead of a lion. The game then cuts to a scene of a theater stage, where a play begins starring Momo, a young girl who gets super-powers. At this point the game puts the player in command of Momo. Rather than playing a hero who must save the world, the setting is that of a live stage show (set at the "Namco Theater"), and players actually play as an actor who is merely playing the role of Wonder Momo. This game also features voice samples (in Japanese).
As Momo, she can only attack using kicks, and in doing so builds up her "Wonder" meter. When she touches a cyclone icon or spins by herself, she can become Wonder Momo and can also attack using the Wonder Hoop, which can be reused as long as she is Wonder Momo. After the Wonder Hoop is thrown, she won't be able to throw anymore, while she'll have to wait for it to bounce back to her. Her most powerful move is the Wonder Typhoon, which shoots a lot of small waves of energy toward the left and right simultaneously while she spins.
When Momo jumps, players can visibly see her panties. Also Momo needs to be wary of a photographer in the audience who is determined to get a peek under her mini-skirt. If he is successful, Momo will be stunned for a short time. Additionally, one of the images that appears on the curtain (at the beginning and end of some stages) is Momo wearing only a towel.
Source: Wikipedia, "Wonder Momo," available under the CC-BY-SA License.