When the heavenly whippet looks in Charlie's records, his mother and father are named "Loni" and "Burt", and look like canine versions of Loni Anderson and Burt Reynolds (who were together at the time.)
Steven Spielberg was going to be the executive producer of this film and have it released under the Amblin banner, but left the project after creative differences with director Don Bluth while they were making The Land Before Time (1988).
The illustration on the War and Peace book that Charlie "reads" to Anne-Marie has the caption "General Pomeroy is shot." This is a reference to lead animator John Pomeroy, who is also a military history buff.
The book on Charlie's life reads Charlie B. Barkin September 13, 1937 mostly German Shepard but also part collie, part great Dane and part retriever in short a bit of a mutt. the rest is difficult to make out but may mention how he doesn't have much goodness or loyalty, tends to be on the greedy side, but a a small section does mention strong love.possibly foreshadowing his change from bad to good.