This is another mondegreen I've collected. Last night I heard someone say "She's an heiress".

What they actually said was "She's hilarious".

This is another example of Steve Pinker's observation that the phrase the listener hears is often less plausible than the actual utterance.

The person being spoken about is indeed very funny, but I'm pretty sure she isn't an heiress. However "heiress" was what it sounded like to me.