Speculah:Puellae Magi Don't Age
This speculah was first spotted in animefan's comment on Steel's blog post about Episode 7. Whether it is his original theory or not is unknown.
The theory basically says that Puella Magi, due to the "zombie"-like nature of their bodies, stop aging the day they make the contract. The explanation given in the original comment is that rather than the original body becoming soulless, it is "replaced altogether by a magical meat puppet that approximates her old body appearance", though other explanations for the same basic theory are also possible.
- Kyouko Sakura gives most evidence:
- She speaks in an "arcane" dialect of Japanese; however, characters using strange speech patterns or dialects isn't uncommon in anime (still, it's a fair point).
- In her memories in Episode 7, she is seen in clothes of Victorian style, while not looking significantly younger; moreover, some events in these memories indicate a different age, like the water bucket; however, the highly stylized nature of the memories scenes may mean it is not a valid evidence. On the other hand, she was also shown, in normal animation during her memories, to be wearing modern clothes before her contract with Kyubey, thus dispelling the possibility of her born before the late 20th century.
- We never see any hint of her going to school, which might mean she's graduated; however it's also possible that since she came from a family that could barely afford food, it's why she's not going to school.
- Kyouko is also able to use her Soul Gem's magic to keep Sayaka Miki's body from going cold/decomposing after death. While this isn't outright defying the concept of aging, it comes rather close.
- In the concept art showing a younger Kyouko and her family, Kyouko and her sister are wearing fairly modern clothes; however, the art is not within context. However, a shot in Episode 7 shows the younger Kyouko drawn normally; her outfit is distinctly modern, detracting from the theory that she is centuries old.
- Homura speaks about seeing many Puella Magi die, and trying to stop girls from becoming Puella Magi many times, implying that she's doing it for a very long time - yet she passes as a 13-14-year-old. Not to mention about her Intelligence as shown in episode 1. (In Episode 10, it was revealed that she simply saw the same Puella Magi die multiple times due to having traveled back in time multiple times due to her wish.)
- In the retrospect scene of Mami making a contract with Kyubey in Episode 3, she appears to be of the same age as she is in the current timeline, while she is said to be a long-time and experienced Puella Magi. However, it's worth keeping in mind that "long time" for a Puella Magi could just mean a few months, or maybe just a year, and in that timeframe Mami wouldn't have changed enough for it to be noticeable.
- Near the end of the final episode, Homura is seen in what some have interpreted as a post-apocalyptic wasteland of the far future; this must be taken with a grain of salt, though, since it's pure speculation.
None of this evidence can be considered a hard proof, though.
A possible variation of this theory is that every Puella Magi can choose herself whether to age or not. It can be further variated that they are not aware of that choice - it may be linked with the decision not to feel body pain (about which Kyubey was talking to Sayaka in Episode 7's pre-OP scene), for example.