There are some events that occur worldwide that Backyard Monsters recognized. For example, in an event on Halloween, they gave 100 Shiny and some Halloween decorations in 2010. On that event, there was a huge pumpkin that gave you a choice to open it. If you opened it, the pumpkin will release a D.A.V.E. nuke and your yard will explode (but that's only a joke).
However, sadly since support has been dropped for Backyard monsters, there will most likely not be any future events (Barring the weekly Hunt-For-Krallen event) unless Kixeye decides to breathe new life into the series.
For the full list of events click the image below.
Wild Monster Invasion
Wild Monster Invasion • Wild Monster Invasion 2 • Monster Blitzkrieg •
Monster Madness • Creature Carnage • Brukkarg War •
Creature Carnage • Monster Blitzkrieg
Trojan Horse • Hunt for Krallen
Other and Future Events
Halloween • 50px Raise the Dead