Yep, the only mind altering drug, or somewhat mind altering substance coffee has to offer is caffeine, which is a stimulant indeed.
When caffeine is drunk or taken in the right amount, it can be pleasurable i guess in the sense that it can improve altertness, focus, and give a bit of an energy boost and motivation to "take on the world" and get things done.
I find that caffeine is best used for myself when i have awaken from a good nights sleep and enjoy a good cup of coffee when getting ready to start the day off, or if not coffee, an energy drink. This is where i find they work best. On the other hand, i find caffeine to be ineffective when i am already tired, burnt out and i just flat out need rest.
1L of coffee? That amount is likely to cause OVER-stimulation, and in people like me, it just makes my stomach uncomfortable, like butterflies and a little nausea, tremors, anxiety, jitteryness, and sweating. Not a pleasant feeling, and this is often followed by a "crash" period, where the user feels even more tired and wore out than they were before they used the caffeine in the first place.
As for the kid tripping out? No. If he was "high" and had to be taken to the office because of it, it was likely due to the kid being sensitive to caffeine (most kids are) and it caused him to just act a fool in a hyperactive shot for attention.