Carlin became one of Carson 's most frequent substitutes during the host 's three - decade reign .
During this period , Carlin became a frequent performer and guest host on The Tonight Show , initially with Jack Paar as host , then with Johnny Carson .
Carlin became one of Johnny Carson 's most frequent substitutes during the host 's three - decade reign .
During this period , Carlin became a frequent performer and guest host on The Tonight Show , initially with Jack Paar as host , then with Johnny Carson .