Channel spell vs untargetable?
For this recent example, is 
Fiddle's drain supposed to continue working on an 
Elise that's repelled in the air and supposed to be untargetable?
2 Comments
Yes. Leash spells continue through being untargetable. This includes Fizz E, Vlad W, Elise E, Zed R, Yi Q etc. The same goes for any DoT spells that still have effect even if you are untargetable like Ignite, Swain E, Malzahar E etc.
Keep in mind that Zhonya isn't just untargetable though and it actually makes you immune to damage for the duration (so you can survive ignite etc. by using Zhonya, but can't by using untargetable spell).