Actually I take back what I said. You should avoid doing a prank not because it would be wrong to do at a wedding, becaus your ideas suck and I don't think you are a natural prankster.
Whoopie cushion - a loud farting noise followed by an embarrassed groom and a crowd politely not acknowledging it, meaning he is blamed for a loud fart that is never made clear to have been a prank.
Bugs in ice - obviously not real bugs, who the hell actually finds a bug in their ice cube. People look at them thinking "thats strange" but the desired laugh-out-loud group of people circling around the ice cubes will never happen.
Firecrackers - loud explosions startle everyone, but nothing actually causes any laughter. It isn't funny, just surprising.
Whoopie cushion - a loud farting noise followed by an embarrassed groom and a crowd politely not acknowledging it, meaning he is blamed for a loud fart that is never made clear to have been a prank.
Bugs in ice - obviously not real bugs, who the hell actually finds a bug in their ice cube. People look at them thinking "thats strange" but the desired laugh-out-loud group of people circling around the ice cubes will never happen.
Firecrackers - loud explosions startle everyone, but nothing actually causes any laughter. It isn't funny, just surprising.