Like its genetically enhanced characters, the ''X-Men'' franchise has experienced a mutation. ''X2: X-Men United'' boasts a $120 million budget -- a full $45 million more than 2000's ''X-Men'' -- and it shows. From metal-bodied Colossus to metal-nailed Lady Deathstrike, the sequel is packed with the most mutants seen anywhere short of the Springfield nuclear power plant. The film's scale is bigger, concluding with a near-biblical flood, and the stakes are higher: A major character dies. The deceased party's identity will remain secret here, but be warned: Other spoilers lurk in the following A-to-Z guide to the summer's first big movie:
A is for Shawn Ashmore, the teen-heartthrob-in-the-making whose small ''X-Men'' role as Bobby Drake (a.k.a. human freezer Iceman) is expanded in ''X2.'' When not helping out Wolverine by frosting his warm soda, Bobby dates Rogue (Anna Paquin), whose very touch could suck the life out of him. Talk about a freeze-out.
B is for Oscar winner Halle Berry, who has a little more to do this time as weather-controlling Storm. But without a romantic interest -- or any other pressing personal issues for her character -- Berry's biggest acting challenge remains capturing the right ''I'm using my mutant powers now'' expression.
C is for Daniel Cudmore, the newcomer with a small role as Colossus, a metal-covered giant of a mutant who's a favorite with fans of the ''X-Men'' comic books. Colossus doesn't have much screen time in the movie (and seems to have lost his Russian accent in the transition), but the one scene that shows off his powers scored ecstatic applause in advance screenings.
D is for Bruce Davison, the veteran actor who reprises his role as the mutant-hating Sen. Robert Kelly -- sort of. Actually, the senator's death in the first movie was real, and shape-shifter Mystique has adopted his identity permanently. But will she run for reelection?
E is for evil experiments, which new villain Stryker enjoys inflicting on mutants. He turns his own son, Jason, into what he calls ''Mutant 143'' -- a creepy wheelchair-bound dude whose brain excretes mind-controlling fluid. More popcorn?
F is for Famke Janssen, whose Dr. Jean Grey could hardly close a door with her telekinetic abilities in the first movie; now she can stop cruise missiles in midair. The change, along with other events in the movie, suggests that Grey is on her way to becoming the near-omnipotent demigoddess Phoenix, which was her fate in the comic books. The next step is turning into the villainous Dark Phoenix, which means ''X3'' may already have a plot.
G is for Gambit, a favorite ''X-Men'' character from the comic books who does NOT appear in ''X2,'' despite early reports that suggested at least a cameo. The energy-controlling hero's real name, Remy LeBeau, does appear at one point in the film, but you'll have to watch for it.
H is for Hank McCoy (a.k.a. blue, furry mutant the Beast), who pops up in human form to discuss mutant issues on a cable news channel. Now that's ''fair and balanced.''
I is for Sir Ian McKellen, who, as magnetically gifted Magneto, manages to escape his all-plastic prison. After trying to destroy them in the first movie, Magneto and pal Mystique fight alongside the X-Men in the sequel -- for a while.
J is for James Marsden, who is absent from most of the film as uptight team leader Cyclops, since the bad guys capture him early on. He and Wolverine (Hugh Jackman) keep butting superpowered skulls, but eventually resolve their differences when tragedy hits them both. How's that for a hint?
K is for Keely Purvis, a young actress who appears as a freaky little girl tormenting Professor Xavier. But she's actually just an illusion manifested by Mutant 143. Her spooky surround-sound whispering (''Kill them. Kill all the mutants'') will no doubt have a geek near you doing imitations.
L is for Liberty Island, the setting of the first movie's finale. The characters frequently refer to it and other first-film events, which may perplex those who haven't rented it lately. So, as with ''Lord of the Rings,'' a little preparation doesn't hurt. (Hey, that's why they invented DVDs.)
M is for protean baddie Mystique (Rebecca Romijn-Stamos), who has more aliases than Sydney Bristow. One notable scene sees her attempting to seduce Wolverine by morphing into his crush, Jean Grey -- and then into Storm and even the teenage Rogue. To his credit, Wolvie just says no.
N is for Nightcrawler, Alan Cumming's blue-skinned, teleporting, German-accented mutant, who debuts in ''X2.'' Each disappearance and reappearance is marked by a familiar sound effect (transcribed in the comic book as ''BAMF!'').