Lyra Heartstrings, occasionally called simply either Lyra or Heartstrings, is a female unicorn pony who frequently appears as a background character and occasionally in more prominent roles. She has a magic mint coat, brilliant cyan mane and tail with a white streak, sunglow eyes, and a cutie mark of a lyre. The word "heartstrings" refers to deep feelings of love or compassion and is commonly used in the phrase "tug at the heartstrings" which means to cause strong feelings of affection or sympathy.

Design, development, and production.
Lyra Heartstrings shares her design with Amethyst Star, Diamond Mint, and Lemony Gem. Her mane style is the same as Rose's and Silverspeed's, and she shares her tail style with Royal Ribbon. Her color scheme is the same as that of "Skyra". She has the same cutie mark as other ponies from the current generation and previous My Little Pony generations. Respective examples are the Earth pony Lyrica Lilac and the G3 Earth pony Bee Bop.

Part of Lyra Heartstrings' name, Lyra, was given by fans before it was adopted officially by Hasbro. Her name first appeared in merchandising as Heartstrings in the accompanying pamphlet of a mystery pack toy released in Europe in January 2012, and was later expanded to Lyra Heartstrings in a Playful Ponies toy, a trading card, the mystery pack toy's U.S. release, another mystery pack toy, a mobile game, a board game, a dog tag checklist, and a collectible card game.

According to a layout artist on the show, background ponies are nameless, but Lyra Heartstrings was labeled "Incidental Unicorn #2" at the studio prior to being named in merchandise and other media and has still been labeled "Incidental Unicorn #2" at the studio as of May 22, 2013. The same layout artist has used Lyra for background gags,[9] such as jumping excitedly, drinking from a cup, or sitting like a human on a bench. Sweetie Drops and Lyra Heartstrings frequently appear together, a pairing explained by the artist to be mostly coincidental and based on aesthetic considerations, as far as season one is concerned. The artist has referred to Lyra and the Earth pony variant of Lyra with moderate cerise eyes as the same pony.

Regarding the Alicorn variant of Lyra Heartstrings in the IDW comics'

My Little Pony: Friends Forever Issue #7
, colorist Heather Breckel stated on July 9, 2014 "Tony drew it, I just thought it looked like her" and "I have no idea if it was intentional or not, and was in the zone when I colored it so I didn't think anything of it. I just like putting Lyras everywhere :yay:", and editor Bobby Curnow stated on July 10, 2014 "That would be a mistake!"

Concurrently with G4, a G1 version of Lyra Heartstrings has been introduced in IDW Publishing's Transformers vs. G.I. Joe Issue #13.