Penny acts appalled when Bernadette suggests that Penny's family ate her dead pet pig, because he was "beloved member of the family". However in The Proton Transmogrification she states without much emotion that she used to have a pet pig, but when he died they didn't have a funeral, they had a barbecue.
The guys make thermite in an attempt to remove the stuck lug nut. They attempt to ignite the thermite with a match. Thermite cannot be lit with a match or a fuse. Thermite burns at over 4000°F and has an ignition temperature of over 3000°F. A match burns around 1100°F.
Leonard refers to tortilla chips as "pure hydrocarbons soaked in fat". They do not contain hydrocarbon (like petroleum products), but rather mostly carbohydrate.
Howard is removing the wheel nuts in an incorrect manner. He has removed them before loosening and jacking up the vehicle. If you remove them before jacking up the vehicle, there's a chance the wheel could slip off and the vehicle could drop to the ground.
Sheldon states that lever should be pronounced as lee-ver, rather than leh-ver by using "sleeves, not slevs" as a comparison. Sleeves and lever have different E/EE vowel structures.