I guess about 25 years, then. Probably since somewhat after it aired initially because I didn't precisely follow Simpsons closely, but somehow the phrase "It's a perfectly cromulent word" stuck in my mind - roughly about that time seems right. To be honest I had a memory of it being Calvin in Calvin and Hobbes, and that was my cultural exposure reference, but I guess I misremembered at least that part.
In any case, you English-native-speakers are to blame. If you make up words out of thin air it's no wonder us secondary-language speakers think they are real words when we hear them on American TV.
In any case, you English-native-speakers are to blame. If you make up words out of thin air it's no wonder us secondary-language speakers think they are real words when we hear them on American TV.