Comedic Underwear Exposure
Not even Kamen Riders are immune to this trope.

"I see London! I see France! I see [Insert Name Here]'s underpants!"
Traditional children's rhyme accompanying such an event

Classic comedy trope. A character's underwear gets exposed while other people are present, usually by accident, and much to their embarrassment. Generally involves Stock Underwear, especially Goofy Print Underwear. This trope is primarily for comedic intent, catching a character in their most embarrassing state. Often this is the result of Defeat by Modesty.

Compare Marilyn Maneuver for a specific situation in which this happens.

Alternative Title(s): Standing There In Underwear, I See London