In Switcheroo! players start off with a hand of 10 cards that they are trying to get rid of: the first player to shed all their cards wins. It's a party game that can cater for largish numbers playing as teams but can equally be played with just two, and it plays fast regardless of numbers because players' turns take only 10 seconds.
The cards display either a letter or a 'subject'; for example, 'Something you can see in the sky' or 'something found in a salad'. Each game starts with a randomly selected letter and subject card. On your turn, you play a letter and say a word that starts with that letter and which satisfies the subject requirement. Alternatively, you play a subject card and switch the subject - giving a word that starts with the displayed letter and which matches your newly selected subject.
There are a few 'wild cards' that give a special effect (giving a player an extra turn; giving more time; switching turn order or switching hands) but the core of the game is coming up with words where the initial letter matches the subject. The game comes with an obligatory 10 second sand timer, but the game is sufficiently fast paced that you will probably find you dispense with this as unnecessarily fiddly.
Speed of play and flexibility over the number of players make this an ideal filler length party game. We've been playing, and we're showing here on Board's Eye View, the 'Mini Game' version, but University Games and Endless Games also publish a big box version. The Mini Game comes with 142 cards (77 subject cards, 58 letter cards and 7 wild cards) but that has proved to offer ample replayability. Our one gripe was that it can be a little awkward fanning and still being able to read a full hand of 10 cards.