Magma Dragoon's attacks are an obvious play on the Shotokan techniques used by Ryu, Ken, and Akuma from the Street Fighter series. He's even wearing Akuma's beads! (look carefully around his neck.)
To Ghosts 'N Goblin fans: do you think the battle with General (as either character) looks awfully familiar? It's a little homage to the final boss battle in Super Ghouls 'N Ghosts! The battles even play similarly (both bosses' weak spots are their heads, and you have to use platforms to reach said weak spots).
The PC version of this game has the battle themes for the three phases of the Sigma battle reversed from the console versions (the "heavy metal" version plays on the first two phases, and the evil one for the Ugly Head Sigma phase in the PC version).
In Frost Walrus's stage, if you look carefully in the background of the first part of the stage, you can see Blizzard Buffalo (from Mega Man X3) at the beginning of the stage, and then later Chill Penguin (from Mega Man X) in the mini-boss's room!
The intro and ending songs in the Japanese version were both performed by J-Pop singer Yukie Nakama. Many consider the Japanese songs to be quite a lot better than the instrumental tunes that replaced them in the U.S. and European versions (though I have no problem with them myself).
Bad english or just playfull use of a language? you be the judge! these are the original Japanese names for the bosses
Magmard (magma in the usa)Dragoon, Frost Kibatodos(walrus), Jet Stingren (stingray), Slash Beastleo (Beast), Web Spidus (spider), Cyber Kujacker (peacock), and Storm Fukuroul (owl).