Maybe the podium starts to fall apart (a la Castleween), or even catches on fire and starts to burn away (that would be a little dark, lol). Borrowing an idea from a Fair level I posted a while back another possible end game would be a fireworks celebration that starts going off, but the fireworks explode around the same height as the podium, so it creates a lot of bomb-like blast radii to physics people off of the podium.
As an add-on to this idea, replace the first throwable item (fish/mooncake/rubber chicken/etc.) with either Olympic medals or trophies. 😛