Wolverine appears here side-by-side with Captain America. He's referred to as Howlett. This is based-off the Marvel Comic The Wolverine Saga where it's established his real name is James Howlett and initially he takes the name "Logan" to hide from the authorities in the late 1800's. He later takes up the name "Logan" again.
Logan prior to becoming Wolverine appears to fight alongside Captain America. Sporting both his trademark sideburns and catchphrase "Bub" his name is never uttered.
Captain America's introduction to the series was a vague reference to Cap joining the Avengers in the comic book until "The Avengers #4".
Scott Menville plays Bucky, Captain America's sidekick. Menville is best known for playing a similar role as Robin in Teen Titans and Teen Titans Go!
The portal opened by the "Red Skull" is to Bifrost and Asgard, where fellow Avenger, "Thor" is from - only 40 yrs earlier.