Ultra Bee

The mighty Ultra Bee is the combined form of Bumblebee, Sideswipe, Strongarm, and Grimlock. Drift is the sword.

History
In King of the Hill (Part 2), when the Bee Team dogpiled Heatseeker to keep the Stunticon from firing missiles at a nuclear waste disposal site, he fired anyway. The combination of the explosion, ambient radiation, and the Crash Combiner Stunticon at the bottom of the bot-pile resulted in the Autobots being fused briefly into a combined, unconscious form, which quickly wore off.

In The Great Divide, during the pursuit of Dragstrip, a methane explosion triggered a second merging. The confused Autobots were eventually able to stand up, but decoupled once again when they fell over. Bumblebee later asked Fixit to come up with theories on why they might have combined, and he suggested it was a result of the radiation they absorbed from the nuclear waste site.

In Get a Clue, Fixit later ran tests on Sideswipe and Grimlock to try and determine the nature of Ultra Bee's combination, but only succeeded in getting the two Autobots stuck together, much to their annoyance.

In Out of the Shadows, he later managed to briefly fuse Sideswipe and Grimlock into a "Sidelock" combined form, with Grimlock, to his annoyance, still on the bottom.

In Disordered Personalities, further experimentation resulted in the entire team body-swapping instead of combining.

In Guilty as Charged, Bumblearm was eventually made as the first successfully proper combined form.

In Combine and Conquer, Team Bee successfully fused into the Ultra Bee Team Combiner to battle Menasor, using Fixit's combination machine while it was hooked up to a satellite's power source. However, after the battle was over, Fixit discovered the device wasn't plugged in, implying the combination happened on its own.

In Moon Breaker, the bee team formed up to the Ultra Bee and took on Menasor in a final battle on Earht's Moon. After a short fight, Ultra Bee came out on top.

In Freedom Fighters, the bee team fused Ultra Bee to fight Galvatronus on Cybertron. Though Galvatronus appeared to have the better of Ultra Bee, they were able to gain the upper hand thanks to Cyberwarp who hesitated in continuing to fight. This enabled Ultra Bee to deliver the final blow and separate Galvatronus.

Trivia

 * While this combiner is, in fact, named "Ultra Bee", he is never referred to exclusively as such in the show. Every time Ultra Bee is named on-screen, it is as "Ultra Bee Team Combiner" (or "Ultra Bee Team Combiner form").