I had one great-grandfather who was supposedly brought over by HIAS, even though HIAS insists that they didn't bring over anyone in those days, and that they helped immigrants only after (or when) their ship reached the U.S.
I had another great-grandfather who supposedly entered using the name of the person ahead of him on line, after hearing that person be admitted. The story is that he didn't think he'd be allowed in if he used his real name, so once he repeated the name of the person ahead of him, because he knew that name worked for that person, so it would work for him too. This is impossible for several reasons. First, you gave the name you were using (whether it was yours or not) before you knew whether the person ahead of you in line would be admitted or not. Second, there would be a record of two individuals who arrived on the same day and ship who both used the name that he supposedly used, and I haven't found one. Third, the decision about who to admit or reject weren't based on their names,; the inspectors didn't have access to records of their previous times in the U.S. (the supposed reason he feared rejection under his real name). Finally, the inspector would have been suspicious about hearing the same name twice in a row and checked the manifest to see how many passengers had that name, seen that only one did, and caught him in a lie.
Camarillo, CA, USA