Hey guys, I have thought about this theory for a long time and have just decided to share it with some of you.
Notes: The theory states that the episode's chronological order are not the same as the episode's number.
Section 1: Origin
In a world where Earth is filled with anthropomorphism and non-anthropomorphism animals. The world is similar to ours, where technology took over and the animals lived decent lives. However, one difference between their world and ours is that their world is guarded by a god-like figure we'll call 'Splenday'. Splenday has supernatural abilities and manages Earth everyday, he has a son named Splendid who was really reckless with his inherited abilities. Splenday wanted Splendid to stay away from Earth as he doesn't trust his son. One day, Splendid decided to prove his old man wrong by visiting Earth and attempting to somehow proof he's worthy and all that cliche. He then gets distracted by an acorn and does...whatever you think he's doing to it. Then, he heard a young girl screaming for help and the episode Helping Helps takes place. If you've seen the episode, Splendid failed miserably. After the episode, Giggles' Mother eventually notices that Giggles is dead and...either fell into depression or commits suicide. Splenday then became extremely mad at Splendid and kicked him out of his home(which can be anywhere from space to simply on Earth). Splendid then felt really bad about the whole ordeal and decided to make up for it. He used a lot of his energy to find another planted in space and proceeded to turn it into a habitable place. He then proceeded to revive Giggles and erased her memories related to the original world, including her mother. This would explain why Giggles' Mother never appeared in any of the future episodes. While there, Splendid also found 2 best friends who were killed in the middle of the street. He resurrected them and sent them to Earth 2 along with Giggles as well, those 2 were Cuddles and Toothy . Now, Splendid needs some help and he decided to sneak back to Earth 1 and find someone who is extremely intelligent.
TL;DR: Splendid is actually the god of an alternate Earth that our characters live in.
Section 2: The extraordinary intelligent anteater
Splendid was able to sneak back to Earth 1 without Splenday nor any other god noticing. (Note: I'm just gonna use 'god' for now, they don't have unlimited power and only manages Earth 1). Splendid looked for collegians, politicians, scientists and even child prodigies but non of them were good enough. Splendid was lost, but then he decided to think outside of the box and looked at the homeless shelters. As the flying squirrel explore each one of them, he found, and you guessed it: A blue anteater named Sniffles. He was only a child yet from Splendid's observation, Sniffles has outsmarted many citizens and gaining food to survive. Now, Sniffles IQ was roughly equivalent to Einstein's. Splendid then, well, kidnapped him and brought him back to Earth 2. He gave Sniffles a house that contained a basement full of tools. Sniffles was very confused and scared so Splendid erased his memories and gave him fake ones. He then manages to double Sniffles' already high IQ and flew off. Sniffles then made himself at home and in a few days, he accidentally knocked over a glass of milk. Sniffles decided to create a time machine to fix it and the episode Blast From the Past took place.
TL;DR: Splendid got sniffles into Earth 2 to help him manage the place by doubling his already high IQ.
Section 3: The creation of Lumpy
Now, Splendid used up most of his energy on the previous tasks, but he needed a guardian for the 3 children he rescued. He, without thinking straight, used the remaining of his energy to create a blue moose and named it Lumpy. Due to splendid using a low amount of energy to create Lumpy, Lumpy came of as having a low IQ. Splendid tasked Lumpy on taking care of the kids and flew of to fall into a big sleep. Cuddles and Toothy lost most memories but remembered being best friends while Giggles still has no idea what's going on. Lumpy then decided to take them to a playground which continued the episode Blast From the Past and lead into Spin Fun Knowin Ya (Extra note: While there is a part in the former episode where Cuddles supposedly screamed about dying the same death again, I assume that it was either misheard by the fans or it was simply an Easter egg that has no relevance to the plot). Now, the plot of the episode happened(i.e everyone dies multiple times while Sniffles rewind time constantly in an attempt to save them). Also, when Sniffles time traveled, he went back to a time where Earth 2 was previously habitable before a mass extinction. Now, the episode has lots of time paradoxes but lets just say Sniffles was simply killed by his past self who helped Lumpy, and that's that. After many loops Splendid intervene.
TL;DR: Lumpy was created by Splendid, who looked after the kids but got them and himself killed while Sniffles figured out how to rewind time to save them but ends up getting killed as well.
Section 4: The ability to revive our tree friends easily was created
Splendid woke up from his long sleep and decided to check up on Lumpy and the kids. He was, as expected, shocked to see them all dead, he then noticed Sniffles trying to help lumpy and ended the loop by confronting them. Sniffles told Splendid what happened. Splendid realized what Sniffles has basically invented and rewarded Sniffles by listening to one of his requests, which was to bring some ants for Sniffles to eat. Splendid didn't knew how to create ants so he snuck back to Earth 1 and kidnapped an ant family. Sniffles immediately ate the father ant which started the conflict between Sniffles and The Ants. Meanwhile, Splendid used the time machine and successfully revived the other kids without getting them killed again. Splendid realized that he enjoyed being the owner of an entire planet without his stupid family judging him everyday, so he decided to build Earth 2 by getting more citizens and help them build more infrastructures.
TL;DR: The main reason the characters are revived after each episode is thanks to the time machine that Sniffles created, Sniffles ate the father ant which started the conflict between Sniffles and the Ants.