“Friendship is Magic, but Equality is Power.”  
So yeah, Hearthcards can let you make dual class cards now. Hence why Starlight is a Priest/Warlock. Suits her S5 personality rather well, if I say so myself.
 
Art Source >>1142395 because it’s adorable and the artist needs proper kudos for it.
 
P.S.: The card (as helpfully pointed out in the comments) is meant to read all other minions. So obviously Glimmy wouldn’t murder herself as soon as she’s played. Blame me not proofreading the preview.