Given that both Bioware and PopCap are both owned by EA, a lore writer on Dragon Age: Inquisition decided to have some fun with this lovely easter egg. It turns out Plants. vs Zombies is actually in the game.
This was discovered by Twitter user FioraAeterna (via Polygon), and as you can see, it's about something called Plants vs. Corpses where only a magician can give plants the power to stop the re-animated corpses from taking over.