My favourite official episode was "Jazz In Time", mainly because it had the most changes, aswell as the best (imo) official level "Marinated level". I loved it.

"Tomb Rabbit" being my favourite custom episode has many reasons. I loved it because
-the difficulty just rulez (imo)
-there were several original ideas
-it was very different from any other JJ2 stuff I played
-I liked the puzzles
-I liked the mummies
-I liked the music
-lots more