These are from the "Rocko's Modern Life" episodes "Who's For Dinner," and "Sand in Your Navel."
From "Who's For Dinner":
Virginia Wolfe (Heffer's mom): So, who's still hungry?
Grandpa Wolfe: I say we eat the beaver!
Why is it funny?: Because Grandpa referred Rocko as a beaver (the animal), and it's also a reference sexual innuendo (another name for "pussy" ).
From "Sand in Your Navel":
(after Rocko walks back to the beach, after Gladys Hippo threw him into the ocean)
Rocko: I think she likes me
Random walrus: *to Rocko* Boy, you got a buoy in your pants!
Why is it funny?: Because it's adult joke and another way of saying that guy is having a wet (rhymes with "downer" )
I can't believe Nick missed those jokes when "Rocko" was still on TV.