Why is Letty small and eating Cirno's underware?

Pixiv title : あたい、パーになる！
(Eye'm a Dad!)

Artist comment : 「･･･チルノちゃん、それを言うならパパでしょ。」
(...You just want to call yourself Papa, don't you, Cirno-chan.)

Aww poor daiyousei

Cirno, how could you cheat on Daiyousei and then bring your child to her house!

... ok, enough of dramatics. Daiyousei looks pretty surprised if the plant is any indication

I guess Letty shrinked in the spring.

Not canon, but lulzy.

Does this count as a mid life crisis?

sgcdonmai said:
Pixiv title : あたい、パーになる！
(Eye'm a Dad!)

Artist comment : 「･･･チルノちゃん、それを言うならパパでしょ。」
(...You just want to call yourself Papa, don't you, Cirno-chan.)

Very late response, but パーになる means to "go poof" or for one's head to go blank. 脳天パー means "empty-headed". So more like,

Cirno: Eye went "pop"!
Dai: I think the word you want is "papa", Cirno.