“The course of true love never did run smooth”. Is this a theme of "A Midsummer Night's Dream"?
Good question. Firstly, I'd argue that the whole concept of "true love" is rather undermined by the events of the play. Hermia and Lysander, of course, the "true lovers" (and remember, criticism has largely referred to Hermia, Lysander, Demetrius and Helena as "the lovers") as soon as they get into the forest, have an almost-argument in which Hermia refuses to have sex with Lysander.
When Lysander awakes, thanks to Puck's intervention, he falls in love with Helena, and leaves Hermia. Demetrius, who started off hating Helena, falls in love with her. Lysander says it himself - to Helena:
Be certain, nothing truer; 'tis no jest
that I do hate thee and love Helena.
Of course, Oberon has Titania juiced with the flower - casting a spell that tells her to, whatever she sees as she awakes, "do it for thy true-love take". What she sees is a half-man, half-donkey - and she, so the play implies, has passionate sex with him.
Is it true love? Or is it just magic juice?
"True love" certainly doesn't run smooth in this play: it changes, it's passionate, it's uncontrollable, and it provokes extreme behaviour.
And Demetrius, of course, at the end of the play, is still under the influence of the flower: and he gets married. True love? Or just magic juice? Well - both.