Senbei makes the potion to get revenge over the female police officer Polly Buckets, who was after him earlier in the day. Senbei becomes invisible, but not his clothes. He has to undress completely, but yet he decides not take off his underpants. While seeking for Polly Buckets in the streets of Penguin Village, the invisible Senbei meets Arale Norimaki and her friends who attack him, thinking it is flying underpants. When he finally finds the police officer, the invisible Senbei gets hurt by a Hod Dog van while crossing the streets. He returns to his house three days later, as a "mummy".