Sometime since the last movie Nefario has apparently frozen himself in carbonite, in a similar position to Han Solo at the end of Star Wars: The Empire Strikes Back.
If you saw Despicable Me 3 this weekend, and based on the box office numbers it would appear you did, you probably noticed several easter eggs and in-jokes throughout the film.
The supporting character of Doctor Nefario, voiced by Russell Brand, has appeared in all of the Despicable Me films, but while the character had a significant part in the fist two installments, his appearance here is fairly quiet.
However, did you notice this particular Star Wars reference?