Cubicle Farm Blues: office, Twilight Sparkle, light.
Clowns: circus, Pinkie Pie, dychotomy.
El Kabong Rides Again!: Yup. Crossover. Just in case I can actually make comedy work. Probably not. Regardless, it won't be half as serious as what I'm thinking.
Search for the Sunken City: Sequel to Seagift?
The Adventures of Starswirl the Stubbled and Princess Celestia, Daughter of the King