What is the name of a cross talk about Liu Yong and Xiao Shenyang in Liu Baorui?

The plot you mentioned was not in Liu Baorui's recording, but was performed by his disciple Yin Wenshuo.

The emperor asked Xiao Shenyang what is high, what is low, what is east, what is west, and so on. Liu Yong told Xiao Shenyang: cucumber is high, eggplant is low, melon is east, watermelon is west. ...

The text of this long stand-up comedy can be found online.