For everyone struggling with the BotD:
Collect money from the first 5 waves without upgrading your weapons , only buy Rage from the extra tab and the shop and also Fortify Motel and then don't shoot and let the bunnies attack the base in wave 6. You should build up enough rage to trigger the extra and get the badge after the wave.
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 "Bunny Invasion: Easter Special"){kind=icon}