Cast
Lee Ji-hyun
Romi (voice)
Jo Kyoung-i
Heartsping (voice)
Choi Nak-yoon
Heart King / Monster Truthping (voice)
Yeo Min-jeong
Belita / Girl (voice)
Hong So-young
Stella (voice)
Hong Bum-ki
Dr. Monziu / General Teenieping (voice)
Kim Ha-yeong
Marie (voice)
Ryu Seung-gone
Liam / Butler (voice)
Cho Hyun-jung
Truthping (voice)
Kim Eun-ah
Happying / Young Liam / Girl's Mom (voice)
Jang Ye-na
Lalaping / Maid / Stickping (voice)
Um Sang-hyun
Mr. Bus Stop / Freezeping (voice)