WMG / The Rescuers

The voice (Shelby Flint) singing the somber songs in this movie, is either Penny's singing voice, or what her singing voice will sound like when she gets older.

• Jackie Evancho proves that even little girls can have singing voices beyond their years...
  • Either that or it's merely being sung by a Penny-esque perspective...
  • Perhaps Penny grows up to become a folk singer.

The star of faith was actually Penny's birth mother (and/or father, but it would seem more likely to be her mother) giving her signals of hope or comfort from Heaven.

There actually is a mouse United Nations, the Rescue Aid Society just uses the same room for its meetings.

It would make more sense, after all why would saving troubled humans be such a high priority for mice as a whole?

• Why would it be a priority to the mice as a whole ? Because that's cute and heartwarming.
  • That being said, a more detailed guess: mice happened to attend to a United Nations reunion and found that they were utterly ineffective, and they said that they could do better.
    • P.S.: Your original idea is still a very nice guess.
• IIRC, the charter of the Mouse Prisoners' Aid Society is to comfort prisoners, especially poets, because poets have spoken well of mice in their poetry. And Miss Bianca in particular has a soft heart, and can't bring herself to leave children in danger.

Continuing from above, the Rescue Aid Society is not bound by any UN and or Human governments.

Bianca is Hungarian, which was Communist-controlled at the time, and yet she's as Aristocratic as they come. Either she's a party elite of the Hungarian Mouse Communist party that can get away with it, or why should the mice care about what humans think?

Of course Kyubey contracted with Penny at one point.

Or at least in another timeline.

Her Witch form might be Albertine. Albertine's imagery suggests that she was young, and perhaps rather lonely. Plus Albertine obviously liked drawing, and one scene prominently showed a drawing of Penny with parents.

Penny from The Rescuers and Jenny from Oliver and Company are related.

There's a rumor among Disney fans that Jenny was supposed to be Penny in The Rescuers. And had Penny (or Jenny) been made into an Action Girl instead of a timid little kid, The Rescuers would've done much better. But in the absence of that, it's entirely possible the two girls are related. Their names are one letter off, both are a Friend to All Living Things, and both find themselves in need of rescue from Ax-Crazy villains, courtesy of sentient animals (note, a couple of mice and a street animal gang with a kitten for a main character, hello)! Considering that Jenny is a bit older and don't look much alike (Penny's a blonde, Jenny's a redhead, Penny has brown eyes and Jenny has blue), it's likely the two girls are cousins. Penny, who was adopted at the end of The Rescuers, was likely taken in by Jenny's possibly less wealthy uncle and aunt. Both girls even live in New York, and both possibly live in Manhattan.

• It should be noted that Penny isn't all that timid; she has apparently tried to run away more than once, isn't very afraid of the alligators OR Mr Snoops, does a snappy imitation of Madam Medusa, and has parts of an escape plan already put together. (Also, I think Penny's hair is closer to light brown than blonde.)

Penny and her adoptive mother are related.

Ever notice how Penny's adoptive mom looks like a grown-up version of Penny? What if they're actually related and she just so happens to be Penny's aunt or older sister? Or perhaps even Penny's biological mother? She could, for example, have given her up for adoption as a poor single mother and then ended up adopting her own daughter (not necessarily consciously) as a married woman with an improved life situation?

Bianca has psychic powers.

Hence why she chose Bernard to be her co-agent when he had no experience of being an agent

The Rescuers takes place in the same universe as Chip 'n Dale: Rescue Rangers and maybe The Great Mouse Detective and other films with these movies' mice such as Cinderella.

The usage of common manmade items for the small folk is just like in Rescue Rangers.

• (This is actually because "Rescue Rangers" was originally supposed to be a The Rescuers TV series until the executives said that The Rescuers wasn't popular enough to get a profiting TV series, and that it would work better with Chip'n'Dale. There are some things left of it — including the name.

The Devil's Bayou setting and plot of The Rescuers was inspired by Eaten Alive! (1976), or vice-versa.

Despite being very different films in production around the same time and released in the same year (one being a lighthearted Disney children's animated film with some dark elements, and the other being a less critically-acclaimed adult horror film directed by Tobe Hooper of The Texas Chainsaw Massacre and Poltergeist fame), they both feature homicidal, psychologically unstable villains whose lairs are located in creepy bayous, with pet crocodilians that end up turning on them at the end of their respective appearances. Of course, Eaten Alive was also inspired by a real-life case as well.