Hardhead sings karaoke. (1987)
The very erratically-edited opening fight of the Beast Wars episode "Dark Designs". No other scene in the show ever attempts the same "shaky cam" effect. (1996)
The full combination sequences for the Energon/Superlink combiners are seen only once in the whole show...in the non-canon 'tournament' episode. (2004)
Bumblebee attended Haillee Steinfeld's live performance of her single "Back To Life" (2018)
"Instruments Of Destruction" had its lyrics 'censored' for use in the 1986 movie.
the interactions between Purple Wicked Convoy and Shockwave in the Generations Selects manga reference Akane and Alexis Kerib from SSSS.Gridman. (PWC is repurposed from SG Optimus, who Akane was designed after, while Alexis Kerib and Shockwave share a voice actor) (2020)
the 2007 comic adaptation of the 1986 movie adds in an additional scene of Omega Supreme, Superion and Defensor duking it out against Bruticus and Menasor at the Ark, justifying why they weren't there during the movie. (2007)
the commercial for the Armada Unicron toy uses footage from the 1986 movie instead of Armada. (2003)
the two mutant creatures from the Animated episode "Survival Of The Fittest" are drawn in homage to G1 Pretenders Bomb-Burst and Submaruader. (2008)
Wreck-Gar throws his own G1 vehicle mode at Bumblebee. (2008)
Bulkhead turns his kibble into a chair. (2008)
Optimus Prime tears off a fake head the Decepticons placed on top of his body to control him. (1985)
Several Cybertron toys were redecoed and re-released as part of the 2007 Movie toyline, reportedly due to the toyline selling so well more product was needed to meet demand. (2008)
in the Japanese dub of Animated, in addition to their personalities, Slipstream also tells us what the names of Starscream's clones are. (which is notable, as the names of the clones are never actually said in the original english version of the show)
To make sure her performance as Slipstream was sufficiently Starscream-y during recording, Tara Strong would have Tom Kenny read her lines first, allowing his delivery and intonation to inform her own. (2008)
Where Slipstream got her colours from was debated within the fandom, with the most frequent guess being G2 Ramjet. However, when contacted about it, Derrick J. Wyatt revealed that her colour scheme was actually "loosely inspired" by the Godmaster Overlord. (2008)
MP-05 Megatron was designed in only twelve days by Takara designer Hisashi Yuki. (2006)
Hisashi Yuki was VERY proud of how he designed Car Robots God Fire Convoy to have Fire Convoy and God Magnus "shake hands" as part of the combination, so much so that he personally requested the animators of the CR show include it as part of the combination sequence. (2000)
Ultra Magnus has the honour of being quoted in scientific literature. (2011)
a flashback in the Cybertron episode "Balance" depicts four "wise elders" who are based on G1 Optimus Prime, Rodimus Prime, Ultra Magnus and Jazz. (Jazz appears to have door wings ala his G1 toy, that he didn't have in the cartoon) (2005)
Sky-Byte's ingenious disguise. (2001)
the CGI model of Revenge Of The Fallen Devastator was so big and complex he caused ILM's hardware to explode. (2008)
artists Art Marcum and Matt Holloway pitched a WW2-era TF movie spinoff called Operation Skyfire, and drew lots of concept art for it. The plot involves Skyfire teaming up with soldiers to deal with Nazi Pretenders trying to un-freeze Megatron during the Pacific War. (2014-2016)
Fortress Maximus tears his own head off to prove what a chill, peaceful guy he is. (1987)
Japanese voice actor Hiroki Takahashi voiced Starscream in Beast Wars II, and Optimus Prime in Animated's Japanese dub. Reportedly, while voice recording for that series, his body would still react involuntarily to the mention of Starscream's name. (2010)