What the show means to me and popularity: This show means absolutely everything to me. I can't put it into words, let alone a single paragraph. Every single thing about SpongeBob, I love, you heard me: I love every episode, every episode is perfect. There is nothing wrong with this show. I study fiction for a living, and after avoiding SpongeBob throughout my childhood due to it being banned, it changed my life and saved me. The animation, the characters, the longevity: Everything about this has details beyond belief and it's a treasure trove for someone who practically lives with literature. Every character I can see, hear, feel, smell and taste (lol). It touches upon my senses like no other piece of fiction other than Harry Potter or How to Train Your Dragon. I've never seen the likes of it being able to create such well, fleshed-out characters, and I think this contributes to your 2nd and 3rd questions. While SpongeBob was an insane success during my childhood, its endurance speaks volumes about the quality. Never did I ever think it would last this long. Never did I ever think I'd be making a 25th Anniversary YouTube video gushing about the show and how much I adore it. I've seen every episode up to all of Season 13 so far and a ton of episodes of Kamp Koral, and Patrick Star Show. The show simply never disappoints me.
Characters:
My favorite character is Squidward. He's simply hilarious. Everything out of his mouth, and even the things he says with just his eyes, I can laugh at. I want to hug him all the time. His pathetic-but-lovable demeanor has created a relationship between audience and character that feels authentic, real, like SpongeBob himself. SpongeBob is a character who is very hard to do by the laws of fiction: He's optimistic, happy-go-lucky... right? Wrong. There are so many more things that make this character as long-standing as he is, some of most namely his propensity for aggravation and always having room for flaws despite his "perfect" image. Yet, he has an outlook on life that we all want, that we can all relate to because it resonates with us to an extent, even if we're a "Squidward". And even if Squidward has a bad name in the business, he never gives up, just like SpongeBob.
Evolution: The show has never stopped evolving... in animation, in methods, in the types of stories they do--seriously, there are so many details shoved into roughly 11 minutes apiece I could write an entire book on each episode. It just, doesn't STOP. From Help Wanted to Cephalopod Lodge, to SpongeBob vs. the Big One, none of these episodes have ANTYHING in common!!!
Where to start the show: Anywhere. I don't care about seasons 1-3. Never did. When I started on the show, I didn't know what season I was in... I simply began with random clips, and the fact that this was enough to prove to me personally the show was great speaks volumes. One of the first episodes I ever saw was "House Fancy", and despite its notoriety, I had no problems on the spot. I introduced my friend first to the episode "Arrrgh!" but proceeded to show them many episodes from all eras of SpongeBob.
Wrap it Up: I'd love to go on, hope I didn't miss anything or make it TOO difficult to read, but I wrote this all realizing I was late for my entry! I couldn't possibly let it slide. I love this show so much, it's unbelievable. I've hardly loved a piece of fiction as much in my life, and certainly not more. SpongeBob, never let the haters get you down. There's a reason you and I are still kicking today, and you are shining brighter than any show on television right now.