Backstory
Our little group of seven adventurers was investigating a recent uprising of an undead scourge in a Druid's grove in the center of Cloakwood, a few days journey north from Baldur's Gate. We were (in all our level 4 glory): A Elven Rouge (me), Half-Orc Monk, Dwarf Psionic Warrior (Pat, for the purposes of the story), Human Wizard, Half-Celestial Paladin, Human Cleric, and an NPC Elven Ranger.

We adventured into the forest, found clues, fought foes, etc., etc. After about a week we discovered an entrance to none other than our first honest-to-god dungeon. Of course, this entrance was guarded by 20 Gnolls, with an Undead Gnoll Fighter leading them. We defeat this troop of adversaries, revive the fallen warriors, and press onward. We entered the dungeon with 5 Potions of Cure Light Wounds, and 3 Cure Light Wounds spells prepared by our cleric. We adventured forth bravely through the dungeon, fighting Zombies and Undead Gnolls, growing progressively weaker as our stock of potions and Cure Light Wounds was growing thin. We had to complete this dungeon in one day, or else the reinforcement army of Gnolls set to guard the dungeon entrance would arrive and lay waste to our pitiful souls.

We entered the second to last room of the dungeon, to find another Undead Gnoll Fighter, with a magic Scythe (2d6 + 1d6 Cold, 20x4 crit.) We survive, wasting the remainder of our potions and all but 1 of our Cure Light Wounds (we have no idea what level the Gnoll was, as our DM refused to tell us, but he had an 25 AC (Armor Class), so yeah, damage was far in-between). At this point, it should be noted that our dice rolls were on the low side, myself averaging between 3 and 17. Also, none of us had rolled a natural 20 on our attack rolls, not that it mattered because you can't crit undead anyway.

The Final Fight
We arrive in the final room of the dungeon, where the boss awaits: Undead Gnoll, class unknown. He wields a sword composed entirely of fire, and a magic staff of some kind.

Butt-whooping ensues.

Our already weakened party, having only Spell left, was not exactly in the best condition to fight, and proceeded to drop one by one.

This is where it gets fun.

Our Dwarven Psionic Warrior, Pat, rolls a 20. Now, for those not in the know, a 20 is a critical hit. Also for those not in the know, as I stated, undead are not affected by critical hits. However, the DM shrugs and allows Pat to confirm (if one rolls a 20, one must "confirm" the crit with another roll of a value equal or higher than the opponent's AC, or else the attack does normal damage). Pat confirms with a natural 20. The DM, sitting upright now, asks him to confirm. Pat confirms with a natural 20. Our party, mouths agape, shriek for Pat to confirm. Pat confirms with an 18, combined with his attack bonus to make a 27, exceeding the Gnoll AC of 25, thus confirming the hit. Thus, Pat essentially scored a Triple Critical on the boss. Again, I re-iterate that undead cannot be damaged by critical hits, so technically nothing should have happened, regardless of the extreme, mad, crazy, sick, ill, borderline phat, dicerolls. The DM is utterly shocked, having never seen anything past a Double Crit, and ponders what to do. Our pleas of, "Dude...triple crit!" eventually sway him to cause the Dwarf's axe to cut the boss in half, rendering him prone on the ground, flailing as we execute free shot after free shot on his undead body.

Yeah, we leveled up, too.