The singer and late night host were tasked on Monday with sticking their hands inside mystery boxes that were filled with slimy or disgusting objects.
Gomez and Fallon then had to guess what they were touching without looking inside the box. Fallon started things off by placing his hands inside of a box filled with raw eggs.
Gomez was more fearless and quickly stuck her hands into the box to grab hair in a shower drain. The game continued on with Fallon having to touch a cow brain and Gomez a toy bear.
The pair ended things by both placing their hands into a pile of meal worms. The singer was taken aback by the smell of the worms.
Gomez also discussed with Fallon her recently released album Rare, her first album since 2015's Revival.
"I think I was holding my breath for four years and then finally I just exhaled," the 27-year-old said.