Here's why Terror the dog hardly featured in The Boys season 1. For the most part, Amazon's live-action adaptation of Garth Ennis and Darick Robertson's The Boys was a faithful interpretation of the comic books. Largely the same story structure was followed, and both versions utilize the same brutal violence, gross set pieces and dark humor. However, the TV series did make some notable alterations to The Boys' story. The Female's origin is more or less completely overhauled, several key comic arcs are accelerated and the Boys themselves are presented as a far less cohesive unit.
Another major change, and perhaps the most upsetting for comic readers, was the absence of Butcher's dog, Terror. In the original story, Billy Butcher is constantly followed by his loyal bulldog companion, who has learned the unique trick of humping anything at his owner's command. With little else to live for, Butcher's bond with Terror is so strong that he'd do virtually anything to keep the dog safe. Quite brilliantly, Terror also gets involved in some the the Boys' fights against rival superhero teams.
Terror doesn't properly appear in Amazon's The Boys, but several allusions are made to the canine. Firstly, Hughie notices Butcher has a dog toy in the back seat of his car and, secondly, a flashback scene reveals that before Butcher became the bane of all superheroes, he and his wife did indeed own a dog.
The Boys' showrunner, Eric Kripke, revealed in an interview (via EW) that Terror's absence was purely a practical move. Describing the inherent difficulties in crafting a show with green screen, stunts, special effects and a fairly large cast of major characters, Kripke claimed that the thought of adding an animal to the mix made the production feel even more intimidating. Certainly, it's easy to see the man's logic. Staying true to his comic incarnation, Terror would've had to feature in almost every scene Karl Urban's Butcher was in, which undoubtedly would've resulted in cut takes, unwanted distractions and filming delays.
Arguably, Terror would've also felt out of place among the live-action Butcher's cohorts. In the comic books, it comes across that Butcher is so confident in his team and his own abilities (as well as the physical enhancements from taking V), that he feels comfortable riding into battle with his precious dog in tow. On screen, however, the Boys are a more amateur outfit and also don't use steroids to compete with their super-powered opponents. For this reason, viewers would always seen Terror as a vulnerable target, taking attention away from more important matters.
Responding to fan concerns, however, Kripke not only revealed that Terror is safe and well in the present timeline of Amazon's The Boys, but has also confirmed that the mutt will make a more significant appearance in The Boys season 2, putting aside his reservations for the sake of giving comic readers a single episode of the formidable Butcher and Terror pairing.
The Boys season 2 is currently without a release date. More news as it arrives.