Ok so in the background of Hammer and Fail pt 2 you can see Paul (the bushy eyebrow dude from the plane) walking in the background for a second while the two groups (Edd's group and EDWARDOOOOOO's group) meeting up to try and get the ghost out

In The Scorge you can see the name tags of the two dues. The one with bushy eyebrows has an upside down name tag that says "Paul" the other has a name tag that says "Patryk" and then when you see the plane, you can see the Red Army's symbol. You can see the same symbol on Tord's robot in The End pt 2

In Fundead when the boys figure out the people were zombies, you can see a zombie Tori (female version of Tord) in the small mob that tips them that they're zombies

When  you turn on the subtitles for english on Saloonatics, one part when Edward zooms off it puts lyrics to Firework by Katy Perry. And then later when Matt punches the cage door it says (ANGRY MATT IS ANGRY) and then LATER the two girls Matt is holding looks like two characters from Undertale

And thats all I can think of right now .-.