Well, Eric Idle played him in the movie rather than Weird Al (Though Al did the Junkion theme song (so to speak); "Dare to be Stupid")
An even better reference is that in his second appearance, when he's facing Soundwave (who is armed with Laserbeak in guitar form and is using it as a sonic weapon) he reaches into his skip and pulls out an accordian and gives it a couple of squeezes, before Soundwave fries it! :)
There's a great transcript of his recent Botcon panel here I LOVE the exchange
Random Transfan in audience - "how did you come up with the idea of Wreck Gar just repeating everything he hears?"
Al "This is a fascinating story, really... I read the script."