[magic_beans]

Apparently Slavic languages can be mutually intelligible. My friend who is Russian had a Serbian boyfriend -- both spoke their native languages to each other and were able to more or less understand.

[ryanianian]

Apparently it's pretty common! Stumbled across this list of mutually-ingelligible languages the other day and lost a good few hours on it.

https://en.wikipedia.org/wiki/Mutual_intelligibility