You don't need to build a brand-new activity for every holiday. The simplest change that brings an event atmosphere to an ordinary lesson is swapping the visual theme — the content stays the same, only the "wrapper" changes.
What a visual theme is
Every activity has a configurable background, colors, and graphic elements from Settings → Visual Theme. The free plan has basic themes; Pro and School plans unlock over a dozen extras, including seasonal variants.
Halloween — review with atmosphere
A regular Biology or History review, with the right visual theme, suddenly becomes "the special Halloween lesson" — without changing a single question. Works especially well combined with Quiz Live, where the visual mood shows across the whole projected screen.
Winter holidays
The last class before a holiday break is hard to keep "normal" anyway — a review activity with a winter theme turns the class into a pleasant wrap-up, not just another ordinary lesson.
Spring
Similarly, for the stretch before a spring break — a season-appropriate visual theme adds a bit of variety in a period when attention naturally dips anyway.
How you switch themes, practically
From any existing activity's editor, under Settings, pick a different theme from the gallery — the change applies instantly, without affecting the questions or content already entered. You can always revert to the original theme.
It's the kind of small detail that costs no extra prep time, but changes how students perceive a lesson — from "another review" to "something different today."