mero-mero
Completely smitten and weak in the knees from love or adoration. You lose all composure because someone or something is just too charming.
💡Seeing a cute puppy — 'I went totally mero-mero over that puppy!'
子犬を見てめろめろになった。
I went mero-mero when I saw the puppy.
She went completely ___ over the newborn kitten.
彼女は子猫を見て○○になった。