The Tesco Value Lemming is the natural evolution of the ordinary lemming, sped up by the effect of nuclear radiation from Tesco's main power source. The Tesco Value Lemming is blue and white, and leaps off doorsteps and low shelves.
Occasionally more daring ones can be bred which will jump off fences, windowsills or use tiny bikes to leap over pits of spikes or flames. They are generally taken as the alpha males of the group, or "shop floor", until the mis-judge a jump and plummet to their death in the frozen foods section.
"I was going to buy a hamster today, but I found two Tesco Value Lemmings for only 99p!"