tagalong
From Longman Dictionary of Contemporary Englishtagalongtag‧a‧long /ˈtæɡəlɒŋ $ -lɒːŋ/ noun [countable] 1 British English something that is attached to and pulled behind something else The tagalong attaches to an adult’s bicycle.2 someone who goes somewhere with someone else We were tagalongs on my parents’ vacations.