Okay, hear me out-

Error gets stuck in the MCU and meets Spiderman, they bond over their webs/strings

-Error claims Spiderman as his son and is kinda overprotective of him. At this point Error knows Spiderman's identity as Peter Parker.

-Error is most protective when Peter isn't in uniform and can sometimes be seen on the outside of buildings Peter happens to be in.

-Error lives with Peter, follows him out of sight, and hisses at people he sees as a threat.

-Error can be found on the ceiling either in a hammock made of strings or scuttling across it.

-When Error first meets the Avengers he sees them as a threat to Peter and strings them up. This, of course, causes misunderstandings and chaos.

-Error eventually warms up to the Avengers and makes it clear that Peter is his and if anyone hurts him Error will murder them.

-"Ya sEe ThIs HuMaN? hE's MiNe, Ya ToUcH hIm I kIlL yA"

-Peter feeds his trash to Error sometimes. It freaked everyone else out the first time it happened in Avengers base.

I might add on to this if I get new ideas