鴨が葱を背負って来る（かもがねぎをしょってくる）

Japanese vocabulary

Meaning: along comes a sucker just begging to be parted from his money; a duck comes carrying a Welsh onion on its back

See it used in real works

• Example sentences from Japanese novels & web fiction (Massif)
• Hear “鴨が葱を背負って来る” pronounced in real videos (YouGlish)