What makes Earthworm Jim games a lot of fun is the excellent characterization of the hero. Like The Simpsons, Earthworm Jim (who was a lowly earthworm until he was one day accidentally given superhero powers) deftly walks the line between slapstick humor and social commentary -- you could even call it subversive. Chris McMullen's very thorough review for Games Domain describes what makes it a must-have:

"EWJ gives a breath of fresh air to the whole platform genre. Instead of taking its cues from Super Mario, or Sonic, EWJ is suitably original. For a start, there's none of this monster squishing, or spin attacking in this game. Jim comes equipped with a big red gun, which he can fire in a number of directions, to dispatch any foe that comes his way. Then, there's his body, which can be used to whip monsters out of the way, or can be used to swing across hooks and ravines. Or should the worst come to the worst, he can use his head like a helicopter to guide himself away from a particularly nasty fall.

There are the usual power ups to grab, such as the Mega Plasma Blaster. Jim's gun does drain energy, but recharges quickly given half a chance. But do you really want to be stuck in the middle of a load of baddies, waiting for your gun to work again? Earthworm Jim 2 adds a little more to the formula. Jim now has a backpack companion, Snott, who can be used either as a parachute, or as a swing to swing himself across mucus encrusted ledges. Yuk! Plus, there's even more weapons, with a homing gun, a big laser, a completely useless bubble gun, and the awesome barn gun. The latter is unfeasibly large, and when used, clears the screen of baddies, and most of the foliage, too.

The levels themselves are inspired, although EWJ2's levels are just a tad better than 1's. Pretty soon after the first level, things get pretty weird. Jim ends up in Heck, Evil the Cat's domain, and is forced to outrun falling rocks, screaming meenies, and sometimes just plain run on the spot to get anywhere. Then, after yet more weirdness, Jim has to guide Peter Puppy to safety, across a number of traps. Only Peter is no ordinary puppy. Get him mad, and he'll turn into a snarling monster, and start taking bites out of Jim. You need to keep close behind him, keeping anything vaguely hostile out of his way, whipping him to make him jump, and so on.

EWJ2 gets even better, with a bonus sequence, where you must bounce little puppies to safety, using a big cushion. Only the puppies are thrown faster and faster, and you start diving to try and catch them. I could go on and on for ages about the levels, there's so much to do, and no sign of boredom or repetitiveness creeping in at all."

With extremely original, inventive, and entertaining levels, numerous surprises, excellent graphics, and smooth gameplay, Activision has done justice to Jim with a righteous conversion, with same mastery that ported Pitfall!, the cartridge original, to the PC. Must-haves!