Plop, plop --- whiz, whiz

Oh, what a relief it is! (I.e., da bowels-clearing equivalent of Alka-Seltzer.)

"Plop, plop --- whiz, whiz" refers to what hopefully happens soon after you take a laxative --- i.e., you copiously expel lumps of poop in a long series of loud splashes in da toilet-bowl, while also urinating profusely (noisy farting optional); you also supposedly feel much more relaxed and comfortable afterwards, da same as da famous antacid promises.