The Smelly Left-Overs deck has 98 letter cards, 2 Burp and 2 Oh Poo cards.
Each player starts with a hand of 3 cards. During your turn you draw a card, then play as many cards from your hand as you can and want, either playing letters to start a word, or adding letters to extend a word already on the table. When a word is finished it is set aside and play continues, starting a new word.
Play continues until the deck is exhausted and no one can play any more letters. The cards remaining in each player's hand is their "smelly left-overs", and the player with the fewest wins. The Burp and Oh Poo cards cannot be played, so they will become part of your leftovers at the end.
A variation is to select a theme, and all words formed must relate to that theme.