Scoob!2020

Daphne:
Who's Muttley?

Dastardly:
Muttley was my partner, my criminal co-conspirator, until... until...

[Flashback begins with a portal to the underworld opening]

Dastardly [voice-over]:
I opened a portal, a back door to the underworld, and through it, a glowing gold vision. [He and Muttley laugh and celebrate, then he throws Muttley to fetch gold for him] As I was about to enter, Muttley insisted on taking the risk himself.

Muttley:
[grumbling] Rasm-Frasm. Ingrate. [He feels a forcefield in the portal]

Dastardly [voice-over]:
I pleaded to him, "Muttley, please don't do this." But no, the flatulent fleabag wouldn't listen to reason.

Muttley:
[grumbles as he enters the underworld through the portal and takes the treasure] Ta-da!

Dastardly:
Good boy, Muttley. Bring it. Yes, yes, come on.

[Muttley is about to return to the ship with the treasure, but the forcefield blocks him from returning]

Dastardly [voice-over]:
But that ticket was a one-way trip.

Dastardly:
Muttley?

Dastardly [voice-over]:
Even if I'd opened a billion portals, he could never come back.

Muttley:
[continues to struggle through the portal with the treasure, then he turns around and sees Cerberus, who is offscreen, coming towards him] Uh-oh.

Dastardly:
Muttley! Oh, no. No! Get out of there! [As the portal is getting destroyed, Muttley continues struggling through the portal, but Cerberus grabs Muttley, thus trapping him in the underworld forever] Muttley! [echoes] MUTTLEY!!!!!!

[The portal is now destroyed as the flashback ends]

Dastardly:
Because Muttley isn't the key.