The theme song in this episode was the original theme that was used during it's original network run. The theme you see on most DVD and in syndication episodes is the syndicated theme for seasons 1 & 2.
ALF's voice was re-dubbed for the flashbacks involving the pilot because his voice was originally much deeper in the early episodes but got higher in pitch as the show went on.This was no doubt done to match his later voice.
The opening credits is different from its normal theme, which includes three new sequences.
This is a classic example of a "clip show." When an episode uses a collection of 'flashbacks' from previous episodes to save time and money to produce a new episode.
It has been said that originally ALF got an electric shock on the bathtub with an electric appliance. That's why his hair is all messed up in the first scenes. But was changed to the "bump" to avoid children to electrocute themselves.