There is a statement in the closing credits: "No raccoon or tree creatures were harmed during the making of this movie. However the same cannot be said for the handlers of the raccoon and tree creatures."
At the end of the credits the disembodied head of David Hasselhoff states: "In these times of hardship just remember "We are Groot!"
Several credits in the closing credits read "I am Groot" before flickering and changing to the actual credit.
SPOILER: There are 5 scenes in the closing credits:
One of the few Marvel Cinematic Universe films to have a full opening credits sequence, which is played over the Guardians battling an alien creature, while ELO's "Mr. Blue Sky" plays.
Cosmo the dog (from the first film), Howard the Duck and Jeff Goldblum are seen in the credits