 "Peggle Extreme", a special edition of "Peggle" bundled with the PC version of "The Orange Box" features levels based on "Half-Life 2", "Team Fortress 2" and "Portal".The headcrab is also an unlockable character in "Super Meat Boy" when bought on Steam.The Headcrab also appeared in an April Fools event in the MMO "Vindictus" as an event item along with the Crowbar, possibly due to the game being created on the Source Engine as well.