If you look at at it, Chibiusa's introduction is absurd. This little kid has the guts to hold Sailor Flipping Moon at gunpoint. The '90's anime did the right thing in completing the absurdity and making it a slapstick episode. Usagi getting tired of her antics and giving her, of all things, a spanking relieves the tension arising from the absurdity of the situation. Crystal played it straight and it didn't work. Usagi later wondering if Chibiusa is an enemy doesn't work either. Usagi thinks with her heart not her head. The end of her '90's debut episode with Usagi tucking her in fits Usagi's motherly characteristics better. (Notice they had her acting like a mom towards Chibiusa before the relationship was revealed? Spanking her, tucking her in.)