#4. Erick Rowan's mystery box angle before his WWE release
In the 2019 WWE Draft, Erick Rowan moved to RAW not too long after his storyline with Daniel Bryan ended. Around November 2019, Rowan began a storyline where he carried a cage that was covered.
The storyline wasn't the best one, but the anonymity of the angle led to some organic interest over what the reveal would be. In hindsight, fans shouldn't be surprised at how WWE handled it.
Erick Rowan was on a good run and had a few squash matches as well in between. It seemed as though he was steadily getting a push, with the cage being covered until March 2020.
Interestingly, current AEW star Fuego Del Sol was once an enhancement talent who took a peep into Rowan's cage before the creature inside attacked him, causing his face to be covered in "blood".
In March 2020, No Way Jose asked Erick Rowan what was in the cage, and Big Red said that all he was waiting for was for someone to ask him nicely. He revealed a big furry spider to be in the cage.
A week later, Drew McIntyre defeated Rowan and squashed the spider in the cage RAW, and a month later, WWE released Big Red from his contract as part of the April 15th cuts.