Lyra

Lyra is a mint-green background pony with a lyre for a cutie mark. She is often seen with Bon Bon and is often shown doing silly things and making funny facial expressions, something that the fans have taken and run with. Also, it hasn't escaped many fans notice that she shows up everywhere Twilight Sparkle goes, even when Twilight's nowhere near Ponyville; for example, Cloudsdale, and not redesigned as a pegasus!

Relationship with Bon-Bon
Several episodes (like Fall Weather Friends and Swarm of the Century) showed Lyra and Bon Bon in close proximity; as a result, the two are often portrayed as lovers in fan labor, and the two have been the subject of numerous pieces of shipping artwork and some shipping stories. The shippings are typically called LyraBon.

Examples of shipping fanfiction that portrays this relationship include Lyra's Melody of Home by Vanderblast, Black And White by Melionos, and The Melting Pot by Katalus Talrius.

Children
After the episode Call of the Cutie introduced several new fillies, and because Lyra attended the cute-ceañera, some of these foals were taken to be children of Lyra's The most enduring of these "fanon adoptions" is Tootsie Flute; fan art depicting the three as a family continues to be made, as of December 2011.

Another filly imagined to belong to the couple was Sweetie Belle, as in this example from three days after the episode aired. That particular piece of fanon was never widely accepted, however, and dashed entirely when the episode Stare Master confirmed Sweetie Belle as Rarity's sister. This comic references some fans' disappointment with this development.

Lyra memes
"I mean, I sit oddly one time to crack my back, and I get a reputation."

- Lyra, from Sepia Tock

After being seen sitting on a bench in an odd manner in the episode Dragonshy, Lyra has become the subject of a number of memes, the most prominent of which is "sitting Lyra".
 * "Sitting Lyra" involves showing Lyra sitting on various chairs and in various other places in the same odd sitting position she was shown in in Dragonshy.
 * "Lyra wants to be human" - because Lyra's sitting position resembles the manner in which human beings sit on benches, it has been theorized that she has an obsession with humans, and would very much like to be one. Examples of this meme include depictions of Lyra running on her hindlegs.
 * "Lyra wants hands" depicts Lyra wanting hands, or actually having hands instead of hooves. It is a sub-meme of "Lyra wants to be human".
 * "Seapony Lyra" is unrelated to any of the above memes, and was started by a picture of Lyra as a seapony, drawn by popular fandom artist johnjoseco.
 * A Lyra plush with a pocket in an unfortunate place launched a new meme in late May 2012. It involves one or more of these plushes used for various purposes, such as a pencil-sharpener, comfy shoes, or a wallet. The meme also extends to images of various people poking out of the hole. The original purpose of the plushie was to act as a sex toy for males. The plushie was sold on The Dealer's Den for the equvalent of $704 June 3, 2012.

Other names
A recolor of the Twilight Sparkle blindbag pony bears approximately the same color scheme and cutie mark as Lyra, but was named "Heartstrings" by Hasbro.

This led to a lot of discussion within the fanbase about whether Lyra should be renamed Heartstrings, or have the name incorporated into her fanon name somehow. The argument for the name "Lyra Heartstrings" was put forward, as was the idea that the names of toys are not relevant to the show itself. Some fans also adopted a number of joke names, including "Fred" and "Incidental Unicorn #2" (both put forward by a layout artist working on the show, and the latter being the internal designation for that particular pony design) and "Harpass".

Equestria Daily's Sethisto encouraged authors of fanfiction to "keep using the fanon names" "for the sake of not driving fanfic archives everywhere insane".

The issue has led to the production of some fan art, for instance, addressing the confusion resulting from the two names (as in this example from the webcomic And that's how Equestria was made), or showing a violent confrontation between "Lyra" and "Heartstrings" (as in these images by `Pyritie and FluffyWuffs), or just reaffirming the artist's preference of the original name (like here). A second toy of the pony was released in March 2012, this time bearing the name "Lyra Heartstrings".

Gallery

 * Lyra image gallery

Fan art examples
