Walking in the water lemming.
Assign Swimmer skill, then Magno boots and let him enter the water (Medieval practice level is easiest to try this). He will keep 'Magno boots walking' in the water and not drowning. Then make him Twister and knock him down with the fan. Lemming will walking in the bottom of the pool, beneath the water surface.
This glitch doesn't work with SNES version.
This one is not a glitch, but a feature. Normally, Twister leans to the left, but on the Mega Drive/Genesis Twister made from left walking lemming leans to the left and Twister made from the right walking lemming leans to the right. Picture is here (left and right Twisters), but Twisters looks little strange on the still picture
On the SNES can not be two or more Twisters at the same time, only one.
Also, Mega Drive/Genesis sprite for the "tallest" walking lemming has trimmed hair. This is just in the Lemmings 2. Original Lemmings game for the Mega Drive has 'normal' sprite with the hair.