The Fans

You didn't think they'd let 'Serious' Sam Stone go off a mission of world-saving importance unaccompanied, did you? Oh no -- Sam is aided in his quest by the finest comany of allies money could buy: The entire programming staff of Croteam, and half a dozen of their most loyal fans!

Unfortunately, they've got the collective combat skills of a wet rag, and wind up trapped by Mental before the mission has even begun.

For some reason, they also have huge, swollen craniums and chipmunks-on-helium voices.

Rescuing the fans element of their number is easy. From your teleport-in position at Hatshepsut, turn 180 and drop down to the left-hand side of the ramp. Open the square stone door (Mega Secret Found!) and out they come, thanking Sam for their release and following him around the map like a gaggle of geese.
I haven't yet been able to make out all of their names, but an incomplete list would be:
Lutrosis
Old Man Murray (proprietor of one of the first sites to give memespace to Croteam when no-one wanted to know about their game)
Booger (the man who lent his voice to Sam -- what a guy!)
Michael
Levelord (for pimping the game engine, I presume. One of his quotes still conspicuously adorns the top the Croteam website)
Wussboy
(Additions or corrections? -- drop me a line!)

The Croteam staff element are a bit harder to free. Their door has jammed shut, and it's going to take some Serious force to shift it... But what kind of a self-respecting hero would leave his creators in the lurch?

The key? Another obscure secret! Climb back up to the top, go right as for as you can. You should see an innocuous looking squre 'pedestal' standing near the corner. If you could get up onto that... Jump onto the low 'handrail' (balustrade? balcony?) next to it (be careful!), and then from that onto the pedestal. Now turn 90o right and leap onto the 'roof'. Look around from you high new vantage point. See that shiny thing down there? It's the super-secret rocket launcher! What a... convenient... conicidence!
(there's also more rocket ammo at the same spot on the opposite side of the temple, but you don't really need it)

Go back down, left side of the ramp this time, and blast that obstinate doorway to flinders. Croteam is free! Rejoice!
Croteam:
Admir
Alen
Damjan
Davor
Dean
Dinko
Pero
Pong (Pongi?)
Roman
Tome

Loot their underground cell and continue you quest, safe in the knowledge that they'll still be around to code you a sequel.

A broad schizm of debate lies over exactly what one should do with one's ever-growing entourage of Croatian computer whizzes and geeks. To all intents and purposes, they're sadly useless. You can try to valiantly lead them though the level to safety (it's like trying to herd cats), but they vanish in time for the next level and don't give you anything. You could turn vengeful and gun them down in an orgy of Frankenstinian vengance, but it doesn't help anything. One particularly cold-hearted forumgoer (name now lost in the mists of time) suggests using them as cannon fodder by luring them out into the desert and having them absorb the fire of the rampaging Biomechs like some kind of ablative armour made from from scrawny flesh and bone -- but what kind of a sick barstard would do that?

Interstingly enough, in the map editor, the Fans are indentified as 'Mental's. Does Croteam know something we don't?

SERIOUS FACT: OldManMurray makes a (double!) encore appearance on the seriously tripped-out Sacred Yards level, much later in the game. Locating him is left as an exercise for the reader.