Thor: Ragnarok villain Hela was originally supposed to have a brief cameo in the original Thor film, according to writer Zack Stentz.
Stentz took to Twitter to participate in the "Marvel twitter confessions" meme thread, revealing that the original Thor script had a moment during Thor's coronation where Volstagg would yell "What the hell!" prompting Hela to turn around and shoot him a dirty look.
In the 1st draft of the script, during Thor's coronation at one point I had Volstagg blurt out "What the hell!" and Hela turn around & glare at him until he said "Sorry; figure of speech." Ash made me take out the joke, which is fortunate given the events of Ragnarok...September 8, 2020
Ashley Edward Miller, Stentz' co-writer and Thor expert, made Stentz take out the joke, which turned out to be crucial considering Cate Blanchett took on the role of Hela in Thor: Ragnarok, which was released six years later. It's unlikely Blanchett would have been cast years before the third film in the series even began production, so a different actor would likely have played her – if anyone other than Blanchett could have done that role justice. Then we would have ran into a serious continuity issue, or at least a re-cast that would have been hard to ignore.
In the same thread, Stentz admits to knowing very little about Thor lore but did a "crash course" and even audited a college course in Norse mythology while writing the script. In a different Twitter thread, he admits to finishing the entire Thor 1 script in three weeks, which is the writing equivalent of travelling on the Bifrost.
The fourth film in the Thor franchise, Thor: Love and Thunder, likely won't have a Hela cameo, but it will have Natalie Portman reprising her role as Jane Foster - well, kind of. Portman will play The Mighty Thor, a version of Jane from the comics who takes on the Thor mantle. Taika Waititi will return as director. We're here for it on both counts.