I had the pleasure of learning OOP with Smalltalk at university back in 2002. They used it as the second language (Lisp was the first) to teach the principles. I really loved it. What I admired most was that you “lived” in your program. Later on, Java (1.4) was taught, but coming from Smalltalk, everything felt cumbersome, especially working with collections. Of all the languages I’ve used in my professional career so far, only Ruby has sparked the same joy.