My favourite episode of the original series (so far) is "Time, Be Still"

Throughout my sporadic viewings of the original Mobile Suit Gundam series, “Time, Be Still”, episode 14, is the episode I’d recently watched. And it’s probably my favourite so far, because it is the episode where we learn that the Gundam can be incredibly vulnerable given the right circumstances.

The episode revolves around three Zeon officers who hatch a plan to destroy the Gundam: Because they only have one Zaku II on hand, they decide to use explosives to try and cripple the suit. Once Amuro and the Gundam inevitably sortie to cover Lt. Matilda, the trap is sprung, and the Gundam’s shield is blown up thanks to a lucky shot at one of the explosives.
THIS is what makes “Time, Be Still” so good: It demonstrates that despite being resilient as hell, having a smart computer, deadly armaments and being able to outgun famed ace pilots like Char Aznable, the Gundam CAN be harmed. It can be damaged and destroyed under the right circumstances, and it’s this idea that further puts the “Real” in “Real Robot”, and is one of the many reasons why the Gundam is such a famous machine.

The rest of the episode after Amuro springs the trap is also really good, as the rush to disarm the explosives is some of the most intense television ever made, proving you don’t need action sequences and explosions to grip viewers and get their pulses pounding. Really, I just love this episode and the idea it brings and the ensuing intensity makes it my personal favourite so far. Too bad they follow it up with the episode with the worst animation (Cucuruz Doan’s Island).

Look up the manga Kidou Senshi Gundam U.c. Hard Graph - Tetsu No Kanba
Or
Mobile Suit Gundam U.C. Hardgraph: IRON MUSTANG

It’s about the same group of Wappa pilots who planted the bombs on the Gundam in episode 14 and the main protagonist is Cuaran from episode 14.