Subverted: Ann shoots Bob with a shrink ray. Bob thinks the ray may have made him shorter (was the doorknob always that high?) but it's actually a prank — his friends are substituting loose clothes and adjusting things around him.
Double Subverted: ...but Anne actually shot Bob with a real shrink ray — it just had a delayed effect.
Parodied: The ray gun shrinks both the target and the person pulling the trigger, thus making the shrinking effectively worthless.
Zig Zagged: Bob is shrunk along with his immediate environment, so Bob doesn't notice. Meanwhile, the normal-sized area surrounding Bob's shrunken surroundings is itself shrunk smaller than Bob, who builds a shrink ray that malfunctions and causes Bob to grow and crush his new shrink ray and everything around it. Bob, now normal-sized again, is stepped on by a giant man.
Averted: The only obvious way into the villain's fortress is through a tiny crack in the outer wall. Bob cannot possibly fit through the crack as a normal-sized person. Bob realizes that the crack in the wall means that the wall is structurally unsound, so he detonates explosives in the crack and enters the fortress through the breach.
Enforced: It's a medical episode in an educational children's program. You need to be able to show how the body works without blood and guts. Shrink ray! Red blood cells aren't "blood," right?
Lampshaded: In order to spy on Anne, Bob decides to shrink himself down and hide in her purse. Chuck finds Bob in the purse and says, "You'll probably get crushed when she rummages around for bus fare. Why didn't you just follow her with a camera?"
Invoked: Bob develops a shrink ray so that he can shrink himself.
Exploited: Knowing that Bob will use the shrink ray on himself, Anne releases ants all over the laboratory to deal wtih him.
Defied: Bob takes the batteries out of his shrink ray before he starts adjusting its settings.
Discussed: Bob is bragging about his new shrink ray. Anne rolls her eyes and asks if Bob has some way of communicating with her once he inevitably shrinks himself and gets lost in the house.
Conversed: Bob invents a shrink ray. Anne breaks in with a special news report — "And tonight, on the News at 10, is your house a death trap for tiny men? Discover sixteen easy ways to protect your shrunken visitors! We'll have more... after these messages."
Deconstructed: Bob shrinks and quickly finds himself shivering from loss of body heat, unable to breathe because the air molecules are too big, and unable to see because his shrunken cones aren't processing enough photons. Also, he's naked.
Reconstructed: Bob doesn't shrink his body; instead, he shrinks a nano-mechanical version of himself that he controls. This mini-android does not need to breathe or maintain a certain core temperature, and its sensors are augmented to adjust for the minuscule scale.
Played For Laughs: Bob is shrunk to the subatomic level and encounters a lone electron. He tentatively reaches out and touches the particle, which explodes into an entirely new universe. Bob has created his own Little Big Bang and become God. His first divine edict: No shrink rays.
Played For Drama: Bob and Anne break up, but Bob is still desperately in love with Anne. In order to get closer to his beloved, Bob shrinks himself down and secretly has himself placed on Anne's eyelash. Anne is heartbroken by Bob's apparent disappearance and she begins to weep. Bob drowns in Anne's tears.