This is how Twilight's Nightmare and The Symbiote bonds with Twilight goes in My Little Pony: Equestria Girls: Rise of the Symbiote.
[As Twilight sleeps and haves a nightmare, the Symbiote crawls to her bed and briefly turns into a head and growls quietly before turning into a hand going down. Twilight starts having a nightmare about Midnight Sparkle. As she has the nightmare, the Symbiote attaches itself to her and starts to bond with her]
Twilight Sparkle: [in her sleep] No. It can't be true. It's not true.
[The Symbiote starts to bond closer to her and finally enters her body as she wakes up and looks at the clock]
Twilight Sparkle: Oh no no no no. I can't believe I overslept.
[Twilight looks at her reflection to see Midnight Sparkle's wings spreading on her back but then her evil alter-ego reveals herself to be behind Twilight. Twilight gasps]
Twilight Sparkle: Midnight Sparkle?! How is this possible? Optimus and my friends helped me defeat you when Thunderwing attacked.
Midnight Sparkle: You, your friends and those buckets of bolts can never truly defeat me!
[Midnight Sparkle laughs evilly as she merges with Twilight. In reality, Twilight jolts awake]
Twilight Sparkle: It was just a nightmare.
[Twilight notices her hand is black]
Twilight Sparkle: What?
[Twilight looks at her reflection to see her entire body is black]
Twilight Sparkle: What is this?
[Twilight feels something strange inside her]
Twilight Sparkle: I feel...wow. This feels good.
[Twilight tests her new abilities]
Twilight Sparkle: What happened to me?
[Sunset and Human Flash Sentry study a piece of the Symbiote]
Sunset Shimmer: The Symbiote?
Flash Sentry (EG): How did it get in here?
Sunset Shimmer: I don't know
[The piece of the Symbiote starts moving towards Sunset and she puts a hand on it]
Flash Sentry (EG): It seems to like Twilight. Don't let any of that get on her.
Sunset Shimmer: Okay.
Flash Sentry (EG): It has the characteristics of a Symbiote, which needs to bond to a host to survive. And sometimes, these things in nature, when they bind, they can be hard to unbind.