I can't be the only person to regard this episode as the apex of the series. With the exception of the first two episodes and the opening credits, the animation in TMNT strikes me as cheap and sloppy. If all of the animation lived up to aesthetic standard set by the fifth episode, I wouldn't feel like my nostalgia for this show was so misplaced.
The show still produced some quality animation even after the first season, but it was still a mixed bag of good and bad. The ones animated in Dublin have been well known to be very cheap and ultra cartoony with rubbery and wobbly movements and April had brown hair and dark lipstick in a lot of these. Episodes like "Cowabunga Shredhead" share similarities with those particular eps but I don't know which studio handled them.
And there was the episodes which I believe were animated by the French IDDH studio in Seasons 3 where the characters have larger pupils and Donatello's colours were lighter that they should have been (don't know why!) Some Season 4 episodes and the whole of the European tour side-season were like this. These episodes were just OK but looked similar to the AKOM animated Transformers G1 episodes with less detailing and shading, They had a lot of animation errors in those ones but nowhere near as bad as TF's!
The European episodes were animated in France. TMS have a good reputation for the series. It's a shame it hasn't been chronicled which animation studio did what.
Just want to add by Season 6 or 7 the animation was more consistent.
The one valid criticism you can make of the 80s cartoon is that the animation was not consistently on model. There were many different animation studios working on the show and they could never draw to the animation model of say Season 7, I use that as an example as that's what animation studios strived for. Ironically TMS clearly did their best to mimic Toei Animation of the first season which means it's still off model although people love the animation style of Season 1 so they love TMS work on the series.