Two characters to be the mundane Greek Chorus. They may or may not be snarky and unlike the Greek Chorus, they don’t break the fourth wall very often (if at all). They’re completely ordinary… Often the best friends of the main character before all the weirdness with aliens, robots, magic, demons, harems, etc.
Some pairs become involved in the plot less and less as the series progresses, especially if the plot becomes more serious. Given what usually happens to people involved in the plot, it’s probably for the best. However, it’s not uncommon for Those Two Guys to also become popular and even iconic characters in the series.