Fullerene-graphene hybrids potentially exhibit unprecedented properties owing to interactive communication between the two units through a linkage. However, most of their discrete molecular structures have been still undisclosed thus far. With the recent rise in the awareness of facile access to molecular nanocarbon hybrids, we showcase novel π-extended fullerenes with a fused pyrazine or imidazole. Owing to the effective planar-curved π-conjugation, their absorption coefficients significantly increased in the visible region. Curiously enough, during the formation of π-extended fullerenes, an in situ generated NH3 molecule was spontaneously encapsulated inside the fullerene cavity. The NH3 molecule then underwent a timed orifice-expansion triggered by its sustained release. This is the first demonstration that fullerene captures a reactant inside, suggesting their potential usage for a sustained dosing and/or material delivery toward postfunctionalization of fullerene-graphene hybrids.