Didn't expect to see those two in same sentence? Actually they were friends, having met on the set of now-obscure Brit film Stardust, which starred pop idol David Essex who I interviewed back then in London about it all (long story). Anyway, here's a fun little video on the night Keith Moon freaked out on speed and someone called Larry to save him. Hagman should have just ordered, "Slap that drummer with a pie that smells."
When he got to his Malibu the house was a wreck--even Keith's dog was high on speed--but Keith was calming down. But Keith did have one request: "Take me to rehab."