Crashed rockets have started appearing in Team Fortress 2's maps. Players have been posting on the Steam Forums with snaps showing battered spacecraft sticking out of background buildings on 2Fort, Badwater and Barnblitz. When taking a closer look using the Source SDK, fans discovered that the cosmic intruders are called Grockets, but what are they doing in TF2?

A similar thing happened recently when doves started appearing in Team Fortress 2 maps. They heralded the arrival of the long-anticipated Meet the Medic video . The Pyro is the only class without a film, but to see a new video appear so quickly after Meet the Medic would require an improbably fast turnaround from Valve, who have previously taken plenty of time to get their other short films right.

The Grockets could herald the appraoch of a new update, but it's only been a month since the enormous Uber Update made Team Fortress 2 free to play . They could also be a promotional tie in with another game launch, or they could be kicking off another ARG. Given Valve's history, it could be anything, but that's not going to stop us from guessing. We've gathered some pictures of the various rocket sightings from the Steam forums below. What do you think the Grockets could mean?