Friends (As of Constructive Criticism)
While as previously, she was one of his enemies, they eventually settled out and have seemed to been getting along somewhat, although don't do too much.
While not being an ally of his, he tends to tolerate Hot Sauce most of the time, although they haven't interacted too much throughout the series.
Enemies (As of Constructive Criticism)
Stop Sign's disliking of M&M is morely based on his side, as M&M is not against him, but Stop Sign is. This is shown in Not Your Forte when he thought that M&M's rap preformance would be a bad idea.
The only time it has been really shown that Stop Sign was against the two of them was during the first challenge, when he caught them both "cheating" and called them out upon it. Although he hasn't interacted with them in recent episodes, it could be possible that he is still against the two of them. (same applies to Pumpkin & Cherry likely still being upset about Stop Sign.)
Previously, Stop Sign was mostly neutral on Yarn as a whole, but starting in Revive and Survive, he had started getting irritated by her for "not doing what he says is right" not to mention the fact that she also against his rudeness throughout the course of Constructive Criticism. Speaking of which, throughout that episode, Stop Sign ruthlessly went on about how "annoying" Yarn was, even with her trying to help their team. He had called Yarn things like "a baby", "annoying", "useless", and "unlikeable"
Again, even with not interacting with him much, he still appears to be against Can, likely for his uninspired attitude, and considering the fact that he tends to blame things on Stop Sign occasionally.