Whoppers rhymes with:
boppers, chopper's, choppers, copper's, coppers, droppers, hopper's, hoppers, koppers, koppers', loppers, poppers, shopper's, shoppers, shoppers', stoppers, toppers
Whoppers sounds like:
wafers, waivers, weaver's, weavers, webber's, weber's, weberg, webers, whoever's, wiberg, wieberg, wipers, woofers