From Guild Wars Wiki
- The Pygmy Hippo was featured during the Nightfall World Preview Event but it was removed prior to release because its model/skeleton was useful for only one creature.
- Crocodiles were placed in the spawning locations used by the hippopotami.
- The Hippo makes a reappearance in Eye of the North (hard mode only): when exploring the areas around Ventari's sanctuary (Arbor Bay), several Aggressive Hippopotamus will spawn; they cannot be charmed.
- Developers need to limit the number of charmable animals for programming reasons (each possible pet means reserving additional data to be available for download in every zone). (Source: Gaile Gray in 2007.)
- The Scribe - September 21, 2006
- Guild Wars Forums - GW Guru - View Single Post - Petition: Reinstate the Hippo