Luma

Luma is a luma who Rosalina has a connection to. In Super Mario Galaxy, Rosalina was some kind of adoptive mother. But there are differences between that and SuperMarioLogan. In the video game, there were thousands more. But in SML, there was only one. In the video game, Rosalina was an adoptive mother. In SML, Rosalina just saw Luma as one particular star that just has something special that makes her unlike other stars. Also, in the video game, Luma and the other lumas were boys, but here, the one luma is a girl.

Rosalina
She is Luma's admirer and, somehow, the only person who understands her.

Mario
Mario somehow got Luma to agree to go in a fancy lamp so Rosalina would be happy in "Mario's New Girlfriend!", so we can safely assume they've had some interaction.

The Sun
In "Mario's New Girlfriend", Rosalina mentioned Luma disliked the Sun.

Luigi
TBA

Black Yoshi

TBA

Bowser

TBA