Basic Trope: A character who usually can't be bothered to even move turns out to be hyper-competent when the chips are down.
Straight: Bob would rather sit on the couch than do any work - but when he works, he works better than anyone else.
Bob sleeps 23 hours a day and solves Taylor Series in the hour he's awake.
Bob is always on the verge of being held back in school, when he has the potential to be a Magnificent Bastard.
Downplayed: Bob likes to sleep in late, but he's the cleverest out of his group of friends.
Bob never had to work hard to learn anything in his life - why should he start working hard now?
Bob can get the job done so quickly, he has a lot of free time in between his jobs.
Bobnote regarding the Magnificent Bastard scenario doesn't have the desire to manipulate people in the usual Magnificent Bastard style, and is Genre Savvy enough to realize that, at least for some, things do not end very well for such characters.
Bob is of below-average intelligence, but makes up for it by being incredibly hardworking and determined.
Bob decides to shake off the laziness during a particularly hellish mission.
Alternately, Bob wants to succeed at whatever it is he does, but the requirements of The Masquerade, his Secret Identity or even just other commitments in his life take time away from his work and he ends up looking like this trope.
Bob only thinks he's Brilliant But Lazy. He's actually Not-As-Clever-As-He-Thinks and Lazy.
Double Subverted: But gets over it.
Bob literally sleeps all day, but when the other characters need him, he wakes up only long enough to mumble the correct plan of action.
Enforced: "We've got this genius character, but we don't want the audience to think he's some sort of egghead elitist. So let's just show that he doesn't care about intellect by making him The Slacker."
Lampshaded: "If you were awake more often, you might be of better use to this team!"
Invoked: "If I just lounge around and make the occasional intelligent insight, everyone will leave me alone."
Exploited: Alice wants to get a better grade on an exam than Bob, who she knows to be smarter than her but lazier than almost anyone, so she points out to him that the beach is nice this time of year, hoping he'll go to the beach, veg out, and not study.
Defied: There's a tough problem to fix. Bob's superiors, knowing his track record, go straight to him - much to his chagrin.
Discussed: "Your son is brilliant, but lazy. He can make good grades if he just applies himself."
Conversed: "So...the guy that sleeps all day is a brilliant engineer?"
Bob's incredible laziness essentially sticks him in a dead-end position. He may be brilliant, but the higher-ups want someone who's dependable.
Bob is brilliant but is seen by everyone is lazy and is treated in a horrible manner.
Bob used to be a hard worker...but constantly underappreciated and overworked, he eventually Stopped Caring.
Reconstructed: Realizing that hard work is valued by society, Bob works his ass off... to get into a position where he can safely get away with being lazy again, as a Professional Slacker
Played for Drama:
Due to Bob's brilliance, he knows how to get what he wants, yet due to his laziness, he doesn't have the motivation to get it.
He cares about getting what he wants but do to laziness crippling his life. He fails to succeed.