Yes, and no.
Momo, Nana, and Celine were all officially introduced to the anime in the S1 OVA’S.
However, as S1 was over 75% original material, and only used chapters from the first 7 volumes of the manga, many of the important plot points were missed.
Celine was originally a giant alien flower that Lala got Rito as a gift (how she got the space flu in ep 24 btw).
Here’s a picture of her plant form, which only made one appearance in the anime, in OVA #4
Towards the end of the original manga series (in volume 15), she metamorphosed into the humanoid girl she appears as in Motto and Darkness.
None of this made it into the anime. (except Lala getting sick.)
Nana and Momo’s first appearance from the manga is depicted in full in OVA #4.
Rito turning into a girl (Riko) also first happens in the OVA’S. More specifically, OVA #1. True story. Saki and Kentaro (the author and illustrator) decided to turn Rito into a girl for the 100 chapter anniversary of the manga.
That’s why Mikan mentions to Yami that Rito is a girl again. She was decently involved in Rito’s first female transformation.