Actress Allusion: Bette Midler (voice of Georgette) currently has a New York City apartment at 1125 Fifth Avenue, so she has same address as her character and probably lived there when the movie was made (unless it's an astounding example of Life Imitates Art).
Sheryl Lee Ralph, the original Broadway Deena Jones in Dreamgirls, as Rita's speaking voice, with Ruth Pointer, one of the Pointer Sisters, as Rita's singing voice.
Richard Mulligan, mostly remembered from Soap and Empty Nest, as Einstein.
Channel Hop: In North America, this film has always been with Disney; however, in most international territories, it was originally released in theatres by Warner Bros., and in other international territories this was handled by United International Pictures. This is due to output deals Disney made for international theatrical distribution.
Dueling Movies: The 1980s were a very tumultuous time in animation. Don Bluth had very publicly split with Disney and started his own studio, which naturally was in competition with Disney. Oliver had two rivals from Bluth: The Land Before Time, which came out on the same day; and All Dogs Go to Heaven, released the following year but also featuring a roguish talking dog and a heartwarming little girl. Oliver did better than either in theaters (though "Time" had the higher opening weekend and worldwide gross), though it's now a somewhat forgotten member of the Disney canon while The Land Before Time and All Dogs Go To Heaven went on to spawn long-running video franchises.
Originally this movie was going to be a pseudo-sequel/spinoff of The Rescuers that followed Penny after she was adopted. You can still see some traces of it. (namely the main character's name being changed to "Jenny").
Marlon Brando was offered the role of Sykes by Michael Eisner himself. Brando, however, turned it down, fearing the movie would bomb.