After the Martial Arts Tournament between universe 6 and universe 7 Bulma and the crew decides to throw a party. Bulma invites Beerus and Whis to the party and tells them to invite Monaka. Of course, he can’t invite Monaka because he knows that Goku will challenge him so he decided to tell Bulma that he was busy.
Weirdly enough Monaka showed up anyway, he was delivering a gift to the party that Jaco had ordered. Almost immediately everybody starts to realize that Beerus lied about Monaka to help keep Goku and Vegeta motivated but Vegeta figured it out as well. The team then agrees to not share the information with Goku but still needed to get rid of Monaka, knowing Goku would want to fight him if he sees him. With the instant transmission at his disposal it was too late and Goku challenges Monaka right away. Luckily, thanks to Hercule creating a suit that looks exactly like Monaka, Beerus was able to fight Goku in his place. This was one of the funny fights because the suit couldn’t withstand the power levels of Goku and Beerus and started to tear in some areas, but thanks to the help of Vegeta and Piccolo all was well.
Whis eventually breaks up the fight and all was going according to plan until Yamcha opened up his big mouth and ruined the secret. Luckily, Goku isn’t the smartest person in the world and he thought that Monaka had the ability to split himself and make himself bigger. Needless to say that everyone just ran with it.