It's universally acknowledged that most anime fillers suck. In fact, some people hate them so much that they skip whole arcs of long series like Bleach, One Piece, and Naruto. While there's plenty skippable filler out there, people who avoid it entirely might be missing out on some good anime filler.
Yes, it might seem unbelievable, but there's actually some genuinely good anime filler arcs and good anime filler episodes out there. While some studios are just filling time until the next chapter of the manga drops, others use the opportunity to further develop characters, fill plot holes, or just have fun. Vote up the filler episodes you love, and if you skipped some of the episodes on the list, go back and watch them – you'll be glad you did.
My Hero Academia has only one filler episode, and some would argue that it's the best episode in the whole series. Everyone's Internships fills audiences in on what was going on with the rest of the UA students while Midoriya, Todoroki, and Iida were facing Stain.
This is great, not only because it's something that viewers are legitimately curious about, but because it focuses on everyone's favorite frog, Tsuyu Asui, and her adventures at sea. Also, you get to witness Best Jeanist forcing Bakugo to straighten his hair. Who doesn't want to see that?
Despite its poor reputation, Naruto actually has some really great filler episodes – so many that it's hard to choose just one. There's the cinematic masterpiece that is the Chikara arc, there's that one arc where Mizuki drinks a potion that turns him into anime Tony the Tiger, an episode where Kotetsu decides he'd rather let himself be destroyed by an ostrich than be separated from Izumo for more than ten minutes... and so much more.
It's hard to choose just one, but let's zero in on "Gotta See! Gotta Know! Kakashi-Sensei's True Face!" – the episode where Team 7 tries to figure out what Kakashi is hiding under his mask. Their guesses include huge, swollen lips, a devastatingly handsome face, and massive buck teeth. After several failed attempts at tricking him into removing the mask, Naruto finally asks outright. Kakashi peels off his mask to reveal... another mask. The comedic timing is perfect, and it's refreshing seeing Team 7 focused on something childish for a change.
Like most long series, Bleach has a lot of filler... and it can be hit or miss. The Zanpakutō Rebellion is frequently cited as one of the best, as it focuses on the Zanpakutō – living swords that form intimate bonds with shinigami.
In the Zanpakutō Rebellion arc, the sentient swords stop obeying their shinigami's commands. It's a great arc because it explores the concept of their agency, and it's also great because of the bad-ass fight scenes.
Cowboy Bebop has more filler than one might expect from a 26-episode anime but said filler is actually pretty enjoyable. One of the best episodes is Toys In The Attic. In this episode, the Bebop crew is being terrorized by an unknown "creature" that turns out to be have been attracted by a fridge full of moldy food.
The actual fear viewers feel for the crew's safety provides a great contrast with the moment that they hurl the fridge out of the space station. The part where Ed eats the creature that everyone was so worried about also makes for a perfect ending.