Famous cartoon historian Jerry Beck) has verbally stated that he does not like the cartoons where Tom and Jerry were friends or at least cordial with one another, but this was the only exception. (This statement was said during his commentary on the cartoon on the Spotlight Collection DVD).
There are six felines (cats), 3 are grown-up & the 3 others are kittens. The names of the 3 grown-up cats (before Tom's meeting with the honest cat, allowing the dead felines in to Heaven, before Tom's meeting with the honest guarding cat, 1st is Butch, 2nd is Frankie, 3rd is Aloysius. Then a bag bounces & then opens, with 3 kittens. The 3 kittens' names are Fluff, Muff & Puff.
The first Tom and Jerry cartoon to be re-released with Perspecta Stereo.
An escalator to the heavenly environs was, and continues to be, a popular rendition of the way up after one's demise.
The feline conductor is a representation of St. Peter, known to be the heavenly gatekeeper. The bulldog devil is, of course, Old Scratch (aka Satan, Lucifer, etc.).