The Age Issue
Bart Simpson is always 10 years old, even if it's his birthday in an episode. It’s the same with Lisa, as she is always 8. However, several other characters ages have ranged throughout the seasons, with Maggie Simpson being anywhere from 1 to 2 years old, and Homer and Marge being anywhere from 36 to 40. Grandpa Simpson’s age has always fluctuated, though it was once revealed that he is over 80. Mr. Burns has been specifically stated as being both 81 and 104 in different episodes, though it has also been implied that he may be anywhere from 118 to 123. Those are just a few of many examples.