两面包夹芝士

Meaning

"杨颜xf" is how Bilibili UP "一只大哈鱼" introduced himself in his drunk video. It's actually a mix of two UPs: story analyst "杨颜同学" and guide maker "小狼XF". Viewers joked it's "homework copying aftereffects" since Arknights players watch both. The real 小狼XF later changed his ID to 杨颜xf as a joke.