a cincea roată la căruță angolul

fifth wheel▼(anything superfluous or unnecessary)
noun
[UK: ˈfɪfθ ˈwiːl̩] [US: ˈfɪfθ ˈhwiːl̩]

third wheel▼(person or thing that serves no useful purpose)
noun
[UK: ˈθɜːd ˈwiːl̩] [US: ˈθɝːd ˈhwiːl̩]