like a pig in muck

Idiom - British - informal :
خیلی خوشحال و شاد

به عنوان مثال :
Look at your sister out there on the field! She's happy as a pig in muck now that she's back in the team's starting lineup again

منابع

• https://www.collinsdictionary.com/amp/english/happy-as-a-pig-in-muck