Stuck on a boss? Well, you've come to the right place! This is the ultimate boss guide, good luck fighting Smithy's minions. :)

Axem Rangers:

Location: Barrel Volcano
HP: Black, 550; Green, 450; Pink, 400; Axem Rangers: 999; Red, 600; Yellow, 500.
Best Team: Mario, Toadstool, Bowser
Reccomended Level: 20
Minimum Level: 18
Strategy: These guys are pretty easy if you have Toadstool equipped with the Lazy shell. Just have Mario and Bowser give it all they got with the Lazy shell and Spiked Link. If everyone's HP is healed, give Toadstool a few hits too, but only if the party is pretty good HP wise, otherwise, keep using Group Hug, or if someone dies, Come Back. Kill Pink first, then Green, then Black, then yellow, then red. (Or you could just kill red) Once that happens, Axem Red will jump backwards onto a big head thing called Axem Rangers. It's pretty much a cake walk there, just keep attacking. The Axem Rangers knows the most powerful attack in the game however, the Breaker Beam, but that's easy to fix with the Group Hug.

Belome 1:

Location: Kero Sewers
HP: 500
Best Team: Mario, Mallow
Reccomended Level: 5
Minimum Level: 4
Strategy: Belome likes scarecrows, so if you can manage to get your hands on a Trueform Pin, equip it on Mario immediately. Belome also has a taste for a certain white puffball, so don't expect to see Mallow for most of the game. Start off by Fire Orbing the heck out of Belome, and wacking him with the hammer. If Mallow is there, just attack or heal up FP points. This guy isn't really that hard at all, and if you manage to get to level six, he's easy with Super Jump.

Belome 2:

Location: Belome Temple
HP: Belome, 1200; Bowser Clone, 300; Geno Clone, 250; Mallow Clone, 150; Mario Clone, 200; Toadstool 2, 120.
Best Team: Mario, Geno, Mallow
Reccomended Level: 18
Minimum Level: 12
Strategy: First off, unequip all of your items and let belome win. This will result in a game over. You will return to the save point, but if you look at your stats. *Gasp.* You have all of your EXP earned! And look! The treasure chest containg the star is still their! Wow! Keep doing that and you will quickly reach lvl 18. Well, now that you're level 18, Belome is easy! Just has Geno and Mallow fight away with their magic, and have Mario keep attacking! Beware though, Belome will make clones of the characters, which has some deadly magic. Not to mention Belome's very annoying sleepy attacks of his own...

Birdo:

Location: Nimbus Land
HP: 777
Best Team: Mario, Geno, Mallow
Reccomended Level: 18
Minimum Level: 17
Strategy: Birdo is quite easy. First crack her egg, which does nothing anyway, then she will pop out and introduce herself. Don't bother with magic, but just keep attacking! The shells she shoots are almost impossible to block, but will ricoche off of the character. Just keep attacking!

Boomer:

Location: Bowser's Keep
HP: 2000
Best Team: Mario, Geno, Mallow
Reccomended Level: 21
Minimum Level: 20
Strategy: Boomer is quite tough, but not too hard. He's got an instant K-O attack which really isn't that hard to block, but leaves you with 1 HP. Just attack with timed hits and magic and you'll get him. After his defeat, you will be taken far up the castle to fight a familiar looking foe, which is were the real battle begins...

Booster:

Location: Booster Tower
HP: Booster, 800; Snifits, 200 (each)
Best Team: Mario, Bowser, Mallow
Reccomended Level: 9
Minimum Level: 8
Strategy: Booster is not a required enemy to fight, but he's fun anyway. First take out his Snifits using timed hits. Then take on Booster himself. Watch out for that Loco Express though, it's a real pain.