After "What We Do in the Shadows" Season 4 kept Colin Robinson in baby and child form, Season 5 has shifted its focus to the energy vampire society that it only now reveals is actually a thing. Apart from Evie, "The Campaign" introduces us to the energy vampires' prevalence in politics, and even brings in the appropriately long-winded and annoying Supreme Council of Energy Vampires. This means that without other major energy vampire characters to back him up, Colin Robinson would have to deal with an entire vampire society arc by himself, which is a tall order — after all, the more traditional vampire storylines have multiple characters at their disposal.
With this new development, it's entirely understandable that "What We Do in the Shadows" brings Evie back since she's the only other previously-established energy vampire character in the show. If Season 5 intends to keep exploring the life and times of energy vampires, fans can probably expect Evie to stick around for quite a while. Her unique, friendly-yet-adversarial chemistry with Colin Robinson certainly adds a breath of fresh air to the show.
