Amy Howler (Mayim Bialik) and Howard Wolowitz (Simon Helberg) in The Big Bang Theory did not have much in the way of relationship, not even purely as friends.
Amy, as you know, ended up with Sheldon and Howard ended up with Bernadette. Of course, Amy and Howard had a couple of episodes centered around them and their mutual love of music in general and Neil Diamond's songs in particular, but that ultimately went nowhere and their friendship was not further developed.
Which is understandable - even in a long-running sitcom, screen time is not infinite, and not every story idea and character combination can be realistically explored.
But some of the fans still believe that this was a huge missed opportunity, because these characters clearly had fun together and therefore the pair's interactions were also fun to watch.
So, the idea that the show should have done something with Howard's and Amy's friendship got quite popular among Redditors, as evidenced by the number of upvotes when it got brought up. While approval was not unanimous, the was along the lines of:
"I think in sitcom-world Howard & Amy make enough sense as friends… …they are both intelligent, curious people who work in STEM, are polyglots and musicians, and share several friendships."
Which means that they have more in common that some of the characters who ended up as romantic pairs (in particular, Penny really had nothing but sheer coincidences and scriptwriters' will making her hang out with the rest of the main cast).
As a result, there is a feeling that Howard often got sidelined, compared to other main characters, and a number of storylines centered around him were set up, and then just… never happened. As was the case, for example, with his unknown brother.
Some fans even believe, based on such cut-short developments, that the showrunners did not like Howard as a character, and after some point tried to use him as little, as Simon Helberg's contract allowed them. Which might be an exaggeration, again, no show can follow every plot hook. But it looks like than with Amy and Howard a genuine opportunity has been missed.