Question

What two franchises joined the NFL in 1950 after the All-America Football Conference folded?

Answer

Cleveland Browns, San Francisco 49ers.
The Browns won the championship in all four years of the AAFC, then won the NFL championship in their first year. They played in six straight NFL title games from 1950 and 1955, all against the Lions and Rams. The Browns went 3-3 in those six games.