!!King's engagement with Bailey will set up a chain reaction of RelationshipUpgrades that will play a part in Keene's quest to fulfill his father/owner's work.
When King and Bailey go through with their marriage, other pet couples will wonder about doing the same. This will result in several similar engagements, including most of the current canon couples, particularly Grape+Maxwell and Peanut+Tarot.

This may have far-reaching implications, particularly regarding the original work of Henry Milton, which Keene has been working on for at least the past year. The pet marriage issue may accelerate this "human-animal reconciliation". With Keene's "deal" with Pete, this may also have a connection to the ultimate resolution of the Cosmic Game.

!!Spo and Squeak are brother and sister.
Spo mentioned that he has a huge family; so huge, his next younger brother is named "Spp".

It's possible that Squeak, Joey's mouse girlfriend, is actually named "Squ", and is actually Spo's little sister.