So I asked a similar question here and that was confirmed. So I want to extend it. Since an eidolon can get close enough to a human pass a disguise check to pretend to be one, just how close can it get? Looking like it's made of clay or porcelain could be called roughly human but anyone who takes a long hard look is going to tell the difference unless it's wearing full body armor or something similar.
The rules for the eidolon's appearance read as follows.
The eidolon’s physical appearance is up to the summoner, but it always appears as some sort of fantastical creature. This control is not fine enough to make the eidolon appear like a specific creature. The eidolon also bears a glowing rune that is identical to a rune that appears on the summoner’s forehead as long as the eidolon is summoned. While this rune can be hidden through mundane means, it cannot be concealed through magic that changes appearance, such as alter self or polymorph (although invisibility does conceal it as long as the spell lasts).
Biped Starting Statistics
Size Medium; Speed 30 ft.; AC +2 natural armor; Saves Fort (good), Ref (bad), Will (good); Attack 2 claws (1d4); Ability Scores Str 16, Dex 12, Con 13, Int 7, Wis 10, Cha 11
Claws, limbs (arms), limbs (legs).
Bodyguard Source: PZO1117
The eidolon looks like a humanoid warrior. The natural armor of a Bodyguard eidolon appears to be a suit of metal plate, though this armor is actually part of the eidolon’s body. Bodyguard eidolons are normally trained in a variety of dangerous weapons.
11 points: Base Form biped; Primary Evolutions improved natural armor, weapon training; Secondary Evolutions ability increase (Strength), fast healing, weapon training (martial).
An unchained Eidolon can do that via a few subtypes ancestor and angel being prime examples which is why I specified chained which from what I've heard is a massive upgrade from unchained.
Ancestor source: PZO9473 Whether created by bonding with the soul of a petitioner that was the summoner’s ancestor in life or calling upon the impressions of such a soul left behind on the Ethereal Plane or the Akashic Record, ancestor eidolons are outsiders cast in the mold of mortals, and exhibit extraordinary skill and talent. They usually appear as idealized versions of the bodies they possessed while still alive, but distinctive and proud. Ancestor eidolons lend whatever aid they can to their summoner, who typically has some form of familial connection with the eidolon, be it by blood, honor, or devotion.
Angel Hailing from the higher planes, angel eidolons are creatures of exquisite beauty. They usually appear in idealized humanoid forms, with smooth skin, shining hair, and bright eyes. Angel eidolons are impeccably honorable, trustworthy, and diplomatic, but they do not shy away from confrontation when facing off against evil and its minions.