Perfect Girlfriend is an episode I realized I liked from a thematic point of view about romance, Independence, sure I thought the episode was a bit cheesy but overall it's grown on me.
Origin stories, did AF/UA really need them, part of the mystique was that the show wasn't in your face with information. We alway's got some information about alien species but the mystery of what we'll never know was part of the fun. Same with the omnitrix, like Dwayne mentioned before it's important to feed those fans who want to know about the omnitrix but don't overfeed them.
This directly comes from episodes like Kevin's Big Score and Absolute Power, we see who Kevin is NOW and the mention who he was THEN but the actions of the present dictate the story.
As much as I liked Nor The Iron Bars and Vendetta, they don't add to much to actually see flashbacks, the mention of them is effective enough. From Kevin's stepdad mentioning he burned there house down or Ben and Kevin's rivalry only mentioned not seen.
Solitary Alignment felt too in your face, but Moonstruck was awesome because it told a story no one has ever mentioned as worked.