In "The Lost Mattress," Tom is revealed to be a mattress salesman at Mattresses & Then Some.

Karen does not have a heart, as stated in a conversation between her and SpongeBob in "Friend or Foe." However, this does not prevent her from expressing emotions or feeling true love for Plankton.

Mr. Doodles is Mr. Krabs' pet worm who appears in the episodes "Sandy's Rocket" and "As Seen on TV" as well as the online game What's Your Bikini Bottom Pet?