Would you like an egg in this trying time?
This is cavegg01.
You may recognize it from the first set of rooms in Artaria, particularly where the counterattack tutorial takes place. This is a muzby egg, and it's the vessel from which muzby grubs are born into the world.
You can see muzby eggs in the background of the tutorial itself. In this shot, they're in the background below the muzzle of Samus' arm cannon.
But that's not all: there's a cavegg02, and—get this—it features two eggs. The smaller one's a bit dented on top, but we pay that no mind: this is a background asset, so we wouldn't notice that during normal gameplay.
Something interesting to note is that the egg models are hollow, likely to save space on the cartridge or to give the game less to render, allowing those cutscene transitions between maps to end quicker.
Wham, double feature! You thought I'd show you the eggs, but not the babies inside them? Nay! Muzbabies be upon you!
The grubs are orange, and their bodies grow pink near the extremities. It has a tiny head, dark pink in coloration, and mandibular structures that remind me of the grubs of real-life goliath beetles. They appear to lack eyes.
When Samus approaches the grubs, they hide behind their large forelegs. Adorable! And smart. These grubbies aren't being eaten today!
The model for this creature is called bigfistgrub. Its textures are simply labeled with "grub". "bigfist" is the internal name for the muzby, which is featured in this article on the official website for Metroid Dread (The website is now down, but fortunately, the Wayback Machine and Wikitroid have our backs!). Given that these babies are called grubs, I'd wager they pupate at some point during their life cycle, transforming into the lumbering pink pals we see in Artaria.
Speaking of Muzby...
That's right! Triple whammy.
Of the humble Muzby, MercurySteam says:
Muzby This terrestrial creature with heavy arms is one of the larger lifeforms on Artaria. It drags its arms behind as it walks. Because it dwells and has evolved in darkness, a Muzby doesn’t have the equivalent to a face. It has tough, rugged skin and high endurance, so high-powered attacks like the Missile or Charge Beam are effective. Samus can also slide between its legs when it lifts its arms to attack.
Muzby may not have a "real" face, but it does appear to have little mouth parts with mandibles in the front. Given the developers' description, I'd hazard a guess and say the muzby is blind. If those spots on its face aren't proper eyes, they may be sensory organs of a different stripe. Perhaps they process olfactory information, or sense heat. Maybe they exist to fool other creatures into thinking the muzby can see them when approached from this end, like eyespots on the wings of the Polyphemus moth?
The muzby also has nubby feelers atop this segment of the body. Perhaps the muzby uses them to sense vibrations in the environment, or maybe these organs release pheromones. Who knows!
The muzby has two huge arms on one end of its body, and a pair of smaller limbs on the other. It carries two pairs of even shorter arms behind the mid-sized set: you can see them curled up behind the animal's small "head".
The article says the muzby has a tough hide, and its exterior certainly doesn't appear to be overly chitinous. The muzby reminds me of a soft-shelled crab in this respect, especially considering the layout of the underbelly.
In-game, the muzby attacks by turning so that its large arms are facing the threat, then rearing up on its hind legs, slamming its big meaty appendages down on the opponent. It doesn't seem to have any trouble navigating in either direction.
Muzby: a beautiful creature with very cute babies!
