3's a crowd is a Caillou episode.
Caillou is at the park with Leo and Clementine when he breaks Clementine's bucket and Leo and Clementine get mad. Caillou then fears that they're no longer friends with him. Caillou tries to do things by himself, such as swinging and climbing on the monkey bars, but no such luck. Caillou's Mommy suggests Caillou to lend Clementine his bucket, so Caillou gives Clementine his bucket, and Caillou, Leo, and Clementine become friends again.