Temporary Superstar

A normal character becomes able to succeed at nearly everything he or she attempts but only temporarily -- usually this lasts only one episode, Story Arc, or equivalent. Can overlap with Superpowers for A Day. This may include taking on some of the traits of a Mary Sue.

When this trope wasn't intentionally invoked, common causes include: a new author got to write the character, he was trying too hard to please the audience, or he just got carried away with his favorite character.

Whatever the cause, expect things to get back to normal pretty fast.

Maybe related to I Just Want to Be Badass and God for a Day.

Comic Books

 * The Incredible Hulk: "General Thunderbolt Ross", normally a supporting character, becomes a Marty Stu  It has stopped recently with new authors balancing the character.

Live Action TV

 * Arguably, the Doctor Who episode 'The Lodger', which is almost a parody of this trope. We see The Doctor jump into the life of average guy Craig- and become immediately awesome at everything. He's better at football than him, better at his job than him, and his crush thinks he's handsome, all without trying. You see what it must feel for the other, sidelined characters when a Mary Sue warps their world.
 * In the Buffy the Vampire Slayer episode "Superstar", Geeky Jonathan uses a magic spell in order to turn himself into a God Mode Sue, with everyone's memories altered to believe he'd always been that way.

Western Animation

 * Kim Possible: Ron Stoppable is normally a likable comic-relief character. In the Grand Finale, he became a God Mode Sue with "mystical monkey powers". According to Word of God, this was an intentional bonus for Ron fans.
 * Winx Club: Bloom becomes this in season 3, when she becomes incredibly powerful for no apparent reason. Her standard transformation is stronger than the other girls' Enchantix transformation. In Season 4, it was leveled down at the same level of her friends.
 * Dib had an episode where he was all-powerful, solved all the mysteries of the world, stopped the Irken armada, was loved by everyone, and got to ride a moose. However, in the end,.