Friends

Krillin and Bulma's friendship is very hilarious, which often lands Krillin into some crazy situations. Krillin developed a trend in making Bulma angry when they first met in Dragonball calling her "Bloomers" in the English version and making Bulma angry about that. Of course, Bulma developed a trend in joking about Krillin's bald head (mainly against the Red Ribbon Army) and that later continued on into Z. I'd say they have a form of "annoying sibling" relationship that provides a lot of comic relief. Krillin actually is scared Bulma (along with Gohan, Mirai Trunks, and Goku) at times, which makes their scenes even more hilarious together.

Krillin and Oolong's friendship is mostly results in Oolong saying some random comment and getting Krillin angry. Actually, I think Krillin only tolerates Oolong because they both live at Kame House. There isn't much screen time between them but when there is, it mostly involves Oolong insulting Krillin or commenting on how he cokes. According to Oolong, Krillin doesn't cook very well.

Dende and Krillin's friendship is not as strong as Dende's and Gohan's but there is strong friendship between the two. Krillin befriended Dende on Namek and the two become close friends after the events with Frieza. Krillin even risked his life by savng Dende from Frieza on the planet by allowing himself to get impaled on Frieza's horn. Krillin is later on excited to learn that Dende will be the new "Guardian of Earth/Kami." Krillin teases Gohan and Dende when they are having a reunion back on the Lookout after four years that he is glad he doesn't have the 'homework' that Dende has in Namekian and Gohan's regular schoolwork.