Octavia is the placeholder name of a background character who makes her debut in The Best Night Ever. She has a dark gray mane and tail, a light gray coat, and light purple eyes.

Appearances

She plays a cello as part of a four-pony musical ensemble at The Grand Galloping Gala. She retains a calm, dignified expression, except when Pinkie Pie disturbs her. At Pinkie's request, the orchestra plays the Pony Pokey. Octavia eventually falls over when Pinkie tries to make her play faster.
Octavia appears again briefly in Sweet and Elite while playing with a different musical ensemble in the garden party to which Rarity was invited. William Anderson, the show's composer, has relayed to Equestria Daily that the music playing in the scene features a harp, two violins, and a cello, which pegs Octavia as a cellist. The show's director, Jayson Thiessen, figures the instrument is a cello as it's "more sophisticated and appropriate for the gala".

A Flash image of Octavia was added to the Hasbro website's Card Creator game around mid-February 2012, named "WhomeverThisIs.swf".

http://www.hasbro.com/common/assets/Flash/Creative/dad2af6e1c4311ddbd0b0800200c9a66/0f6b55af5056900b1013cd724a8d4018/assetsuitcase/characters/MLP_CharV_WhomeverThisIs.swf

Re-use of character model

The character's design is reused with a different color scheme in Luna Eclipsed. Her coat is yellow, her mane and tail are dark blue, and her eyes are light blue. She plays the fiddle in the a pose similar to the one used in The Best Night Ever, though the hooves are slightly altered, grasping the bow and neck of the instrument with the hooves instead of the fetlocks, or "wrists". The rest of the band similarly uses the designs and poses from The Best Night Ever, with different color schemes.