In the beginning Dawn warns Marianne that seeing her intended before the wedding may cause bad luck. A short while later, Marianne DOES see Roland... but he's kissing someone else, thus leading to her cynicism... Although one could argue that this was actually good luck, since she didn't marry a guy who was cheating on her. Good luck for her; bad luck for Roland and his plans.
What's more ironic: the superstition about seeing the bride before her wedding resulted from the belief that if the groom saw the bride before the wedding, he'd get cold feet and bail out. In Roland's case, it wasn't so much cold feet as it was his cheating heart that doomed their wedding plans, even before he saw Marianne.
All of the fairies wear their hair short, even the more feminine girls (as opposed to the tomboyish Marianne), because long hair would be constantly getting tangled in their wings.
Marianne stops the Bog King as he's about to confess his love to her by singing Can't Help Falling In Love, and sings an entirely different song. This is because that song so far has only been sung when the love wasn't real — first Marianne and Roland have a duet before she finds out he's cheating on her, then by the love dusted prisoners. Marianne wants a song that will prove it's real this time.
Speaking of songs being sung, I Can't Help Myself (Sugar Pie Honey Bunch) which Dawn sings while love dusted sounds very cute, but the lyrics actually sound, from a modern view, like a very unhealthy and dependant love. Which fits considering how artificial love from the potion is.
The Love Is Strange song number from Sugarplum is similar. In particular the line they think loving is money in the hand foreshadows just how complex real love is and how the love potion is not an instant cure.
Why is there a random fairy in the Dark Forest to be love dusted when no fairies normally ever go there? The fairy seems to be the girl Roland cheated on Marianne with, and was humiliated in front of the full court when Roland tries hiding from Marianne behind her. It makes sense that she'd want to avoid her fellow fairies.
A couple of sly references to Flower Language:
Roland's pet name for Marianne is "Buttercup." Buttercups symbolize ingratitude, childishness, and a desire for riches, which are all personality traits Roland has in abundance; this also foreshadows his ulterior motives in courting Marianne. Buttercups are also related to primroses (in the context of the movie, symbolic of artificial love). Oh, and they're poisonous.
Interestingly, a Marianne is a type of anemone, which can symbolize a loss of hope and a feeling of abandonment, but also anticipation of something better down the line. That pretty much sums up Marianne's entire character arc.
Primroses can express the sentiment "I can't live without you." Dawn's second song when she's high on primrose potion is basically repeating that line over and over and over again ad nauseam.
Why did Bog want all the love potion victims gathered in one place? Mostly to prevent chaos and make sure there weren't people singing love songs all over his kingdom, but at least one fanfic writer has charitably suggested it was also so that, when/if Sugar Plum made an antidote, they could all be dosed and cured at once.
When the opening song turns into a duet, Roland never actually finishes the line "I canít help falling in love with you" with "you." It subtlety reassures what the audience might already know at that point (that Roland doesnít actually love Marianne) and quickly foreshadows the fact that heís seeing someone behind her back.
The cure for the love potion is True Love...how are they going to find the True Loves of everyone else who was potioned? Won't it be nigh-impossible to get them to even try someone else if they're still under its spell?
What's especially scary is if they're no other's true love: unlike A Midsummer Night's Dream, there is no flower-based antidote to reverse the effects. If you're dusted, you're apparently stuck loving whatever you saw first by force of the potion forever.note Yes, it has to be romantic love because sister-love apparently didn't work. This may or may not be the case depending on the single instance shown.
Depending on whether Lizzy was supposed to be viewed as sentient or a normal lizard, the potion even works on beings that have no concept of romantic love - possibly on aromantic people as well. Dawn was In Love with Love. Consider how unsettling it would be to see someone else forced into lovesick mode.
The snail that fell in love with Pare will probably be following him for the rest of his life, just really really slowly.
The Bog King appears to be out of a house and home after the events of the movie.