Thats weird that you say that because I never liked Unidentified Flying Leonardo. I don't remember why but I remember being unimpressed with it. That and I think I was annoyed with the whole cliche stupid southerners flipping out about seeing crop circles and so-called aliens
What I liked about Leonardo Vs. Tempestra episode is that he actually acts genuanly funny in this episode. I watched this recently and found my self cracking up a few times at Leonardo's reactions. Also I liked the whole "sneaking into an arcade to play video games" at night thing to be very refreshing as opposed to just waltzing into one in broad day light with lame customs on to hide their idenities, which is more likely on what the turtles would do. And heck the turtles even have moment when they act like actual ninjas in the arcade when they are almost discovered by the matinance guy and leave in a moment, then go back a clean up the mess they left in like a minute when the matence guy complians about the pizza boxes. Sweet.
I also liked that this episode actually had Leonardo acting like a teenager playing video games and relaxing with his brothers in stead of him acting in his normal uptight leader role. I like when episodes occasinally deviate from a characters sterotype every once in a while and make them act diffrently.
I also liked the fantacy aspect of the episode and the whole roller coaster and news Van sequence. It was all very nice.