Lamarr

"Lamarr" is a Xen headcrab that appears in Half-Life 2 under the ownership of Dr. Isaac Kleiner. Early on in the game, Gordon Freeman is shocked to find a headcrab running loose in Kleiner's lab, however the doctor assures Freeman that the creature is harmless. Lamarr, as Kleiner calls it, has been de-beaked and cannot take control of a human host.

Half-Life 2
Lamarr's first appearance is in the Half-Life 2 chapter A Red Letter Day, when Kleiner gives Barney the honour of presenting the famed HEV Suit to Gordon. As Barney opens the door to the suit, Lamarr jumps down from the holder, attempts to latch onto Barney's head, and after being removed, crawls around, observing the area. She then jumps up on a locker and into a vent. Kleiner remarks that "it'll be another week before I can coax her out of there". Later, while Gordon is about to teleport to Eli's lab, Lamarr jumps out of the vent and into the teleporter, causing Gordon to teleport randomly to various areas around City 17 and eventually directly outside Kleiner's lab. This forces Gordon to travel to Black Mesa East on foot. Lamarr can be seen briefly in one of the teleported locations, in what looks like a sandy wasteland with a destroyed car. Lamarr jumps away from Gordon (apparently escaping the reflux) to chase after some crows. Gordon then teleports away, Lamarr being too far away to teleport with him. It's possible she transitioned to several other areas like Gordon did, albeit separate from him.

Through whatever means, Lamarr eventually found her way back to Kleiner. She is seen peeking out of the door with Kleiner when Gordon and Alyx appear in the teleportation chamber before scurrying off to hide from the group, presumably frightened, as Kleiner suggests, by Gordon's crowbar.

In her last appearance, she drops from the top of the screen after the ending credits and jumps toward the player.

Episode One
Lamarr is safe and sound in Half-Life 2: Episode One, where she makes a brief cameo appearance, causing further mischief to Dr. Kleiner during his live and unedited evacuation broadcast in City 17 (though the question of how she found her way back to Dr. Kleiner is left unanswered). In this cameo, she is wandering aimlessly around Kleiner's lab, while he warns her to stay away from hot lamps. It is revealed that many Resistance troops are full of disdain for Kleiner (and Lamarr), as one man states: "We're all starving, and Kleiner's headcrab is probably eating grade-A head!".

Episode Two
In Half-Life 2: Episode Two Lamarr goes to sleep inside Arne Magnusson's rocket whilst the door to it is open. Prior to launch, Kleiner notices a "payload anomaly of an extra eight and a half pounds", but not realizing the significance, he and Magnusson dismiss this and decide to launch anyway, sending Lamarr into space. It would seem unlikely that Lamarr survived.

Description
Lamarr differs from the standard headcrab in that the typical black "teeth" are missing. Otherwise, she is virtually indistinguishable from a normal headcrab. Although Kleiner refers to Lamarr as a female, headcrabs have never actually been established to have multiple genders. Lamarr appears to be unable to draw nutrients as a normal headcrab does, instead subsisting on a diet of watermelons—this is indicated by a post-it note posted on a board in Kleiner's laboratory, serving as a reminder to find more watermelon (presumably a favourite for its general resemblance to a human head).

Personality
Lamarr's behaviour may be proof of the ability to "tame" a headcrab. Simply being de-beaked does not suppress the aggressive, parasitic nature found in all headcrabs. Kleiner states that she may attempt to "couple with your head...fruitlessly, of course." Though Lamarr is somewhat wild as shown when she is first met — lunging at Barney, attacking a bird on the rafters, and then escaping into ventilation shafts — she can also be seen walking beside Dr. Kleiner and peeking curiously around a corner, behaviour that predatory headcrabs do not share.