Lemmings are rodents with all the trappings of cuteness: soft fur, short legs, small ears. They are known for their population fluctuations and periodic migrations. It is generally believed that they respond to overpopulation by running off cliffs in a massive suicidal death march.
However, the truth is, although some lemmings have died by drowning or falling off cliffs, there is no evidence that this was done in a deliberate attempt to kill themselves.
So how is such a belief propagated? Well, Disney's 1958 nature film, "White Wilderness," can probably take some of the credit. The producers wanted to include a scene showing lemmings marching to their deaths. Unfortunately it was filmed in Alberta, Canada, which is not a native habitat for lemmings. This did not stop the filmmakers, who purchased up to a thousand lemmings collected by Inuit children and flew them to Alberta (the lemmings, not the children).
According to The Urban Legend Reference Pages, "the arctic rodents were placed on a snow-covered turntable and filmed from various angles to produce a 'migration' sequence." Later, they were taken to a cliff and herded over the edge of the river below.
Lemon Pledge: for polishing off furniture.
Lemming Pledge: for polishing off cute, fuzzy rodents.