Mad Libs, I think, have very limited usefulness with English Language Learners since they really don’t promote accurate understanding. However, for ELLs who are in the high-intermediate range, I’ve found they can be an occasional fun activity that also reinforces parts of speech.
Having students create their own versions for their classmates can move this activity to a much more productive level, however, and the Word Blanks site is the easiest tool out there for making them (Mad Takes is a good site to find already-made ones).
I’ve shared quite a few games I’ve learned from Jimmy Fallon’s Tonight Show and how I’ve modified them for language-learning.
Last night, he did it again!
He created a Mad Lib for a movie scene and then acted it out with Benedict Cumberbatch. The idea of explicitly creating ones that would lead to a performance could be fun as well as just another way to encourage speaking and listening, especially for ELLs with enough proficiency to be able to get the humor.