There's a few things that I wonder if they would qualify for "beam me up, Scotty!", which refers to lines lots of people incorrectly think were said on shows (or misquote, incorrectly combine different phrases into one, or were actually said but weren't said enough times to be a catch phrase but was such a popular line that people think is a catch phrase). I don't know if enough people made the mistakes or if it's the mistake of one.
Anyway, I used to think that in the old Life Cereal commercials, the ending line was "He likes it! Hey, Mikey!" but for years I thought the line was "He likes it! He really likes it!" To be fair I think "he really likes it!" makes more sense to follow than "Hey, Mikey!"
And for some reason my dad thinks that on Happy Days Potsy's catch phrase was "Funny as a crutch, Rich", but I don't ever recall Potsy saying that line on the show. I assume that if he did he said it to Richie, and I've seen most of the episodes from the Richie era (and seen many of the episodes enough times to know them well, though there are some episodes I haven't seen much).
Another one that I know multiple people have made, both in person and online (and I spent many years thinking this myself), at the beginning of the 1997 "Game Boy Pocket" commercial with a group of teenagers and old people bad mouthing each other at the mall, a few people I went to school with and I thought the commercial began with the teenagers saying "Ew! Old people!" I saw one video on YouTube of someone recreating the commercial (as the user couldn't find it on YouTube at the time) and starting with that line as well. But in the actual commercial, the line is just "Old people!", with no "Ew!" in the line.
One of the notable movie misquotations (a.k.a. mondegreens) is "Play it again, Sam." which is not found in Casablanca.
It was Ilsa Lund (Ingrid Bergman) who requested that Sam (Dooley Wilson) play "As Time Goes By":
Ilsa: Play it once, Sam, for old times' sake.
Sam: I don't know what you mean, Miss Ilsa.
Ilsa: Play it Sam; play "As Time Goes By."
Sam: Oh, I can't remember it, Miss Ilsa, I'm a little rusty on it.
Ilsa: I'll hum it for you. [hums "As Time Goes By"] Sing it, Sam.
Sam: [plays piano, sings] You must remember this, a kiss is just a kiss, a sigh is just a sigh, the fundamental things apply, as time goes by. And when two lovers woo, they still say "I love you"; on that you can rely, as time goes by.
Rick: Sam, I thought I told you never to play---
As for Rick Blaine (Humphrey Bogart), he doesn't like to hear "As Time Goes By", because it brings back bitter memories, yet when Ilsa shows up in his cafe, Rick has Sam play it one last time to get the spite out of his heart:
Rick: You know what I want to hear.
Sam: No, I don't.
Rick: You played it for her, you can play it for me!
Sam: Well, I don't think I can remember---
Rick: If she can stand it, I can. Play it!