A lot of people are correct that this episode clearly seems to have been written and probably aired earlier, maybe one of the first episodes after the pilot seeing as the name Gordon is established early in season 1. I decided to look at some other episode lists all the other sources I could find on air dates indicate that this episode aired *after* the flashback episode that included that mating call. I would wager that the script to this episode was written earlier, but for whatever reason this episode aired later even though logically it should have aired earlier.
Therefore, I think the mistake was in the airing of Alf. Hulu is just keeping the episode #s the same as the order they apparently aired. Airing episodes out of order isn't unique to Alf. A lot of other TV series have made errors in the airing order. The original Star Trek series has a lot of episodes that air in a different order from their production dates. There are some more recent shows where I've seen similar mistakes.
Ideally I would like the option to watch the epiodes in production order as well as air date order. Some people prefer to see it in the order they watched it on TV while others would prefer production date order. The problem is that unlike Star Trek, nobody seems to list what the production order really was so while some episodes were obviously in a different order I am not sure what order they were produced.
I am far more annoyed that Hulu can't keep the splices for commercials at the same place that they were intended for TV.