So, Soundwave, having never met any of the other Decepticons (other than a brief discussion with Megatron) was forced to use Decepticons from the memories of Optimus's crew in order to manifest this illusion of a Decepticon invasion. But, of course, there was the notable cameo of Team Chaar + Shockwave. Bumblebee knew Longarm and the Autobot team saw the upper part of Shockwave's body minus the gun. Prowl supposedely practiced Circuit-Su with Oil Slick and Ratchet met him in the first Cosmic Rust attack during the Great War. Any theories on past encounters with Strika and Spittor? I'd say that Optimus, being the academy bot he is, was taught about Megatron's legendary general and simply read up on Strika, but never actually met her.