Can anyone explain to me how the title of my post is confusing? Thanks in advance

You're supposed to say "That **I** made with my sister" unless it was you, other people and your sister. Personally I don't see anything wrong with saying "at the time"

Who is we? And at what time? Both of these are odd.

"With my sister at the time" So shes not your sister anymore? "I just found a fan poster that me and my sister made [back in the day](https://dictionary.cambridge.org/dictionary/english/back-in-the-day)" is probably what I'd say.

something like “just found this poster my sister and I made back then” or “just found this poster I made with my sister in 2012” (or whatever year) would be more natural

The pronoun “we” has no clear referent. “we” + “with my sister” implies at least three people: you, your sister, and someone else. Additionally, “at the time” lacks the context for it to be clearly understood. A reader might infer that you’re talking about when Community was airing on TV, but it’s still not totally clear that’s what you mean by this.

The "At the time" implies that she is no longer your sister.

The way you wrote the names seems odd，only ancient Chinese or Japanese would write word vertically.

"Poster that my sister and I made back in the days of the tv show" seems more logical to me

Everyone has explained why the sentence is wrong, but I'd like to point out that the slogan on the poster also makes no sense. You can't start with "And". The statement isn't related to anything prior to it. It should start "The reasons?" etc. Although that also doesn't make sense. Reasons for what? You've implied multiple reasons for no event. In an odd quirk, if it started with "The reason?" Singular, then it WOULD make sense because the implication is that you're justifying a reason for the show.

You could say: I found a fan poster that my sister and I made back in the day.

I would be willing to bet that OOP is a Russian speaker. In RUssian, "We with *someone* did *something*" is the standard way of saying "I did *something* with *someone*" (*мы сделали что-то с кем-то*). Plus, the Russian word *togda* (*тогда*) can mean both "at the time" and "back then". So the original sentence would have been something like: *Мы тогда сделали это с сестрой .* Literally meaning "we made this with my sister at the time"... ...but actually meaning "I made this with my sister back then". The literal translation is not good English. Remember: about half of the people speaking English on the internet are non-natives.

“At the time” comes right after “sister”, so it will be read as “at the time” modifying “sister”. If she was your “sister at the time” that implies she is not your sister any more. Context should make it pretty clear that you don’t mean it that way, but folks will poke fun at you for it anyway.

"Fan poster" implies another fan made it. Better description would be "i found an old poster my sister and I created"

Also, if you were part of making the poster, how could you have "found" it?

Also as a side note: the amount of people on that sub who are unaware that that poster is referencing the *single greatest* English language film of all time is absolutely shocking.

I just found a fan poster my sister and I made together.

You use “we” before you inform us who “we” is (we, the audience, can glean that it’s you and your sister but it still is a bit weird to read) “I just found a fan poster that me and my sister made at the time” is what I’d suggest changing it to.

"I just found a fan poster that my sister and I made back in the day"

At the time What time?

Is she no longer your sister? What happened?

"A Community poster my sister and I made" would've been sufficient.

Who is “we”? Is your sister not still your sister?

People keep teasing me about the order in which I wrote the sentence "with my sister at the time." But... even though I understand how it would have sounded better if I had reversed "at the time with my sister" or "back in the days", is what I wrote that absurd? It's not like I wrote "with my then sister"...

The idea is understandable but the words “at the time” are just hanging. The description text provides that context but too late.

Thank you all for your answers and advice 🥰 I understand better why people kept teasing me 🤪