What Voyager episode do Neelix and Paris get in an argument in the dining area, which turns into spaghetti/pasta-on-the-heads/uniforms-fun? I want to watch that episode.
You're thinking of 2x07- Parturition:
From Memory Alpha linked above:
After an altercation in the mess hall between Neelix and Tom Paris over Kes and involving hair pasta, Captain Janeway has the two of them to go down to a promising planet in a shuttlecraft to search for food supplies while also ordering them to settle their quarrel.