[This is a rewritten version of a post I made on r/Kirby 8 months ago.]

One day, I came across the following passages in Elfilin’s character entry on TV Tropes (final entry under “Other Heroes”):

Cosmic Motifs: According to the official guidebook, Elfilin’s ears were designed to resemble the waxing and waning of the moon. This was meant to represent “having lost the quality of a single existence”, that is, having separated from Fecto Forgo.

The Fog of Ages: According to the official guidebook, he barely has any memory of his time as a test subject in Lab Discovera anymore.

At the time, I wasn’t able to find anything else that talked about this information. At some point, I checked out this official(? It’s official enough for WiKirby.) guidebook myself. This is the relevant page (it’s also the final page in the preview).

My attempt at a transcription of the relevant passages (I can’t read Japanese):

ともに旅をしながらアドバイスをくれるカービイのパートナー。本人の記憶にはほとんど残っていないが、ID-F86の中に残されていた小さな博愛の心が分離して生まれた存在で、かつて研究者たちには"ID-F87"と呼ばれていた。再び融合することを目論むID-F86によって、とらわれの身となってしまう。

月の満ち欠けをイメージしてデザインされたという耳。1つの存在だったものが欠けたことが表現されている。

Based on machine translations, the TV Tropes descriptions seem pretty accurate. And according to a commenter on the original Reddit post, in the Kirby light novels (separate continuity from the games, so take the implications with respect to game canon with a grain of salt), Elfilin also doesn’t remember Lab Discovera. So that’s some not-so-new-at-this-point-but-still-not-widely-talked-about Elfilin lore for you.