Thunder Slimer is the mini-boss of Spark Mandrill's stage that is encased inside a huge blob.
In both games where he appeared, Thunder Slimer will shoot blobs, making Mega Man X unable to move when he's standing there. Thunder Slimer will move on to a space and will shoot thunder bolts at X. It'll also create a bigger blob to let it go up. Thunder Slimer will then repeat again.
Thunder Slimer appeared in the manga, Rockman X.
- In Mega Man X Collection, Thunder Slimer is green instead of blue.