In 1998, Pokemon took the world by storm. Based on Pocket Monsters which was released in Japan between 1995 and 1996, Pokemon was just about everywhere from the original Game Boy video games, TV anime, manga, toys, trading card games, etc. For those who don't know, Pokemon are monsters that come in all shapes and sizes with all kinds of abilities. Pokemon Trainers travel all over the wold battling their Pokemon; usually for fun, sometimes for prestige, etc. Their biggest trait is that Pokemon can be stored in pocket-sized devices called Poke Balls for easy carrying.
Loosely based on the original Game Boy video games, the first and second seasons of the Pokemon TV series (now called Pokemon Indigo League) follows the adventure of Pokemon Trainer Ash Ketchum and his yellow electric mouse-type Pokemon, Pikachu. They adventure with the tomboyish Misty and her water Pokemon, and the flirtatious Brock with his squinty eyes and his rock type Pokemon. Together they battle the evil (and annoying) Team Rocket, who are always scheming to steal all the Pokemon in the world.
Back in 1998, Pokemon Indigo League was originally syndicated for Monday through Friday broadcast. Eventually Kids' WB picked it up and continued to air new episodes for several more years until 2006. After that new episodes would be aired on Cartoon Network, which is still the case today.
Pokemon Indigo as opposed to the more recent TV iterations offered a bit more episode variety and more character development. It was also one of the first English dubs by the now defunct 4Kids TV. It is entertaining for the most part, but it does suffer many of the problems of an anime that was edited for the US audience of the late 90s including bad voice acting and casting, confusing plot (sometimes), some content edited out due to being too violent, sex-related, seizure-inducing, etc.
Pokemon Indigo League is an easy recommend if you have the nostalgia for it or if you caught a few episodes back in the late 90s. You can catch reruns on Cartoon Network's sister-network, Boomerang. You can also stream it on Netflix and Hulu.