For the inscriptions I picked fonts that might look like a signature for them and a more neutral one for the Episode 100 quote of Derpy about the Doctor’s appearance. Here is a little collage showing all sides of the cup.
The cup continues a series of cups (and possibly concludes the series since that type of cups seems to be out of store) dedicated to pairs of popular background ponies. I had started last year with cups dedicated to Vinyl Scratch & Octavia and Lyra Heartstings & Bon Bon.