So I'm really not too deep into the Half-Life fandom yet (I haven't even beaten HL1- I was getting along nice and well and then I got distracted by Black Mesa because oooohh pretty!) but I can tell- Gordon Freeman is really a child at heart. I mean, sure, he beats aliens to death with a crowbar and blows up tanks and stuff, but he's such a joker.

I mean, start at the beginning of the game, yeah? In Anomalous Materials, you can sneak around the main desk and hit the emergency panic button. You don't... really have a reason for doing this, but you can do it multiple times and, honestly, while the NPCs act startled, they don't seem especially surprised... maybe suggesting that this is a prank Gordon has pulled multiple times?

Also, most of the scientists seem snappish and grumpy and not willing to stop and talk to you. I mean, if Gordon had serious things to say, wouldn't they be more willing to listen? But no. If I remember correctly, one of the stock dialogue lines is something to the effect of "this had better be something important... mmhm, I thought not." So Gordon probably joked around a lot.

And while we're on the topic of joking around, notice how (at least in Black Mesa, I know, I was too excited to get on with the plot to explore much in Half Life), contrary to the scientists' attitudes, the majority of the security guards will pause to "chat" (assuming Gordon actually talks) with you, usually giving a few lines of humorous dialogue.

And finally, my biggest support for this, Gordon's idle animations. I mean,

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he freakin' plays with the snarks. These are explosive alien bugs and he taunts 'em. There are other examples, too- off the top of my head, testing the string of the crossbow (what kid wouldn't want to flick a giant, stretched out rubber band?) and (at least in Black Mesa, I haven't checked in Half Life yet) spinning the... uh... spinny part?... of the Tau cannon (this is clearly a very attractive idle pastime, if fidget spinners have taught us anything.)

Anyway. Yeah. Quick argument for why Gordon is a bit of a jokester.

Also I think something must have happened to Gordon's glasses in the Resonance Cascade, because they're freaking invincible.