The part in "What's the POPIPA" where everyone is referencing their solo song feels like Bokuhika from LL (where all the characters names are included) and this makes me happy.
(Kibou iki no densha de Sing out!
Welcome! Tobe! Hanazono e!
Itsuka no poketto no chokoreito
Minna de wakeatte Heart beat!
Chomama chomamamaji Lovin' you)