In An American Benwolf in London, they failed to keep an eye on Wes Green. Later, they helped Chadwick to find Excalibur in London. When their lives were at risk due to a mutated Chadwick on a rampage causing a flood in the underground vault, the Twin Knights and Sir Morton allowed a truce with Ben's group in order to find a way to escape but promised they'd fight again another day once they got out alive.
Ben 10: Omniverse
- According to Derrick J. Wyatt, the Twin Knights are called Happy/Sad or Comedy/Tragedy due to their masks.