Any father, add prefixes like grand pep for grandfather or step pep for step dad, or grand step pepper depper for your great grand step dad. (the -er denotes respect)
A stupid ass event in a school setting where students are forcefully crammed into a gym and forced to watch dumb stuff while godawful music is destroying the ears of people. The school admins also want you to have spirit in your crime-ridden school that is basically Carcer City but in school form.
What to do: skip it if you get the chance to do so. Either loiter somewhere elsein the building or leave completely.
Robert: Well, whaddaya want to do instead?
Joseph: I don't know, whack it to bad amateur porn?
Robert: Well it is a better use of time than attending a dumb pep rally.
To have sex. To "slip" implies an insertion of a body part into a cavity of another person's body. A "pep" is slang for pepperoni, which is itself an allusion to a penis due to its phallic shape.
Nick: "bruh, how did your date with Jess go?"
Josh: "it was fun man, i can see us gettin down to slip a pep in the future"
Brad: "you old dog, that's good, maybe you two can join Chad and I on a double date"
Josh: "fuck yea fuck yea bruh!"