This contribution to "JAVIR=ERROMAN03" of DeviantArt's "Mermay Challenge" combines 2 prompts on his list: #16 (True Star & Bartleby) and #9 (Princess Grizelda) . While I was doing an image search to try and get their looks right, I noticed that Grizelda had turned into a mermaid in the True and the Rainbow Kingdom episode "Friendship Day". So I drew her and True based on that same design, and even gave Bartleby the same shape mermaid fin.
Hope you like this!

DISCLAIMER:

I don't own the characters, only the fanart.