Animated movie: kid can’t escape amusement park

I never actually saw this movie. I only ever saw a preview of it on TV back in the late 90s but the movie looks like the product of the 80s. It might not even be a movie. A short perhaps? Anyway, it’s an animated something about some kids who go into an amusement park-like place. Supposedly it’s the most fun place in the world. There are rides, lots of food, gambling etc. Eventually one of the kids decides he wants to leave. To do so he has to spend all his money. There is a slot machine near the exit where he has to spend his last coin and he wins the jackpot. I vaguely remember seeing a huge talking animal, maybe a whale, in a military uniform at some point.

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