Once I had a developer use a Meme image as an API response in development.

It was funny, but it was surprisingly hard to explain to stakeholders during demos that this was not the real API response. I think I fielded questions from at least four annoyed/confused people asking why the image was there and insisting that it must be changed before we go live.

I even got follow up emails asking for timelines on when it would be fixed.

So sometimes it's better to just use a real placeholder or something realistic.