In What If #10 (August 1978), The Watcher provides readers with an alternate story where Jane Foster (a highly competent nurse), rather than Don Blake (a disabled physician, the current mortal from of Thor), discovers the enchanted Mjolnir.
The story isn’t too bad and has a lot of Loki action thrown in for good measure. Jane Foster takes up the hammer and calls herself “Thordis” (after a Norwegian pal from nursing school), and proceeds to do battle against evil, saving Midgard in much the same way of Thor did in various installments of Journey into Mystery. Altogether, Thordis proves to be a badass. She ends up fighting Radioactive Man, the rock men of Saturn (a la Journey into Mystery #83), the lava people (a la Journey into Mystery #97), Cobra and Hyde (a la Journey into Mystery #105-#106), the inventions of Tomorrow Man (a la Journey into Mystery #86), and she even joins The Avengers. Odin is thoroughly impressed.
She also beats the crap out of Loki with a serious left hook (and then physically throws him from Earth to Asgard…).
Eventually, crazy times get crazier as Ragnarok kind-of-almost happens and Loki takes the throne (albeit briefly) while the All-Father takes a nap (i.e., Odinsleep). Mangog enters the eternal realm and destroys lots of stuff (a la Thor #154-#157). Everyone fights: Don with an enchanted sword, Sif (who continues to get in the way and get injured), and Thordis, who eventually summons “a storm so Titanic that it wakes up Odin.”
After the dust is settled, Loki is collared, Mangog is dealt with, and Thordis gives up Mjolnir because “ownership of Mjolnir hath ages ago been decreed by Fate.” Don takes Mjolnir to become Thor-proper. Sif and Thor smooch. And Jane Foster, back in mortal form, is heartbroken … she and “Don” were mutually unrequited lovers, but alas, Don is now Thor, and Thor has Sif.
That’s when things get weird. Odin acknowledges Jane’s “valiant deeds” and grants her the powers of an immortal goddess (no formal name, apparently). He then proposes to her – “And in the timeless days that follow, the goddess comes to know the sincerity of Odin.” Jane Foster marries Odin and becomes Queen of Asgard.