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 underwear reveal, usually accidental, much to the character's embarrassment. Generally involves Stock Underwear, especially Goofy Print Underwear. This trope is primarily for comedic intent, catching a character in their most embarrassing state. There's also Cringe Comedy present, as the situation is usually awkward.

Compare Panty Shot. If revealing the character's underwear is used to defeat or incapacitate them, it's also Defeat by Modesty.

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