It's from the Simpsons and that is pretty much exactly the context that it first appeared in! Here's an excerpt from the "Made-up words" article on the simpsons.wikia.com:

When schoolteacher Edna Krabappel hears the Springfield town motto "A noble spirit embiggens the smallest man," she comments she'd never heard of the word embiggens before moving to Springfield. Miss Hoover replies, "I don't know why; it's a perfectly cromulent word".