キルコ「チョキ～♪」
マル 「え？！チュキ～！！！！」
キルコ「ちがうわ！アホ！」

Kiruko: "Scissors!~♪"
Maru: "Eh? Skissors~!!!!"
Kiruko: "Wrong! You dummy!"

The pun doesn't translate well but Maru is saying something in pronunciation between "scissors" and "I love you". The "scissors" comes from rock-paper-scissors.