This example can be used to explain why the smallest of details can be so important when conducting research.
This piece by Dvosrsky summarizes a recently published article that points out a (possible!) major flaw in pre-clinical cancer research using rats. Namely, lab rats aren't being kept at an ideal rat temperature. This leads to the rats behaving differently than normal to stay warm: They eat more, they burrow more, and their metabolism changes. The researchers go on to explain that there are also plenty of other seemingly innocuous factors that can vary from rat lab to rat lab, like bedding, food, exposure to light, etc. and that these factors may also effect research findings.
Why is this so important? Psychology isn't the only field dealing with a replicability crisis: Rat researchers are also experiencing difficulties. Difficulties that may be the result of all of these seemingly tiny differences in lab rats that are used during pre-clinical research.
I think this could be useful as it is an example that students can easily grasp. Rat research is used in psychology, but is used here within a medical context, thus reaching students beyond our psychology majors.
Also, it is always a good time to share this story from The Onion about lab rats...