Princess and the Pea- This is an idea that I've had for awhile now, since most of the Shrek villains have been royalty (Farquaad, Charming) I thought it would be interesting to have the 5th villain be a princess since one hasn't been the main antagonist of any of the movies thus far (Rapunzel in Shrek 3 was just an accomplice of charming) and the princess from this fairy tale has not been seen in the movies yet (I don't count the plays as Canon where she's farquaads mother) I also thought it would be a nice contrast to Fiona from the first film, who wasn't your stereotypical princess while this one would be an evil ruler who leads a villainous army . This would also be continuing the Shrek trope of subverting expectations where heroic characters from fairy tales are portrayed as evil
Morgan Le Fay- One of my favorite villains from mythology, this is the one I'm personally hoping for since I predict the 5th villain will be female (since the last few DreamWorks movies have had female villains) and since she wasn't seen or mentioned in Shrek 3 I think this would be a good way they could bring Arthur back into the plot, and also maybe it's revealed she's who cursed Fiona since its never been revealed in any of the movies at all (and I don't think it was the godmother)
Hercules - While characters from Greek mythos haven't been seen in the movies yet (They were for one of the storybooks) I think this would be another way to subvert expectations and also the fact in most Greek mythology Hercules wasn't exactly a hero either. The only thing that I would be concerned about is they might play him as a rehashed version of charming which wouldn't work. If they went this route I'd cast Ryan Reynolds as the voice. I got this idea from a suggestion I saw a long time ago that suggested Beowulf as a possible antagonist for Shrek
Romeo and Juliet - While Shakespeare characters or any from plays haven't been seen in any of the Shrekverse yet (Although Farquaad was based on Richard III) I think this would be an interesting route they could take. I'm a big fan of Shakespeare so this be another cool way to incorporate his characters into Shrek. Also for the voices I'd cast Christian Bale and Carey Mulligan. The first PIB already had a villainous duo in Jack and Jill but this would be the first time for a Shrek film. Bonus points if Tybalt appears as a good guy
