Season 0 of Happy Tree Friends premiered on null.

Season 1 of Happy Tree Friends premiered on 1999-12-24.

Season 2 of Happy Tree Friends premiered on 2002-09-01.

Season 3 of Happy Tree Friends premiered on 2007-11-02.

Season 4

5.3

.

2013

.

9 Episodes

Season 4 of Happy Tree Friends premiered on 2013-06-14.

Season 5 of Happy Tree Friends premiered on 2006-09-24.

Smoochies are videos of individual characters on Happy Tree Friends dying in different and unusual ways. Usually they involve a prop being used in an unlikely and deadly way. Each Smoochie includes one character that can be given something from three options, all of which resulting in the character dying. After a few seconds of inactivity, the character will do an idle action, such as laugh or say hello.

Season 6. Breaks are short 1-minute or less episodes that act as shortened Happy Tree Friends episodes (The graphics and animation are similar to that from the first to second seasons of the Web series because they were originally intended for G4 in 2005 but were rejected).

Season 7. Love Bites are Valentine's Day-themed short episodes featuring romantic relationships between two characters (male and female), that eventually go wrong with one or both members of the couple getting injured and/or dying. Just like with Kringles, each Love Bite contains a message that it's related to the theme of the short.

Season 9. A spin-off about Flippy, Splendid, and Buddhist Monkey starring in an action series. Flippy stars in W.A.R. (Weapon Animal Regiment) Journal. Splendid appears in Splendid's SSSSSuper Squad. Buddhist Monkey returns to star in more new episodes. The Mole was listed as a character, but he doesn't appear to have a connection with Ka-Pow! now, and, as a note, his episode, Mole in the City, debuted way before Ka-Pow! even existed

Season 10 of Happy Tree Friends premiered on null.

Kringles are special short holiday messages (set during Christmas) released as parodies of typical animated greeting cards. There are currently ten Kringles.