Claim: The TV series Doug and Rugrats both appeared on Nickelodeon in 1991.
Evidence: August 11, 1991 (1991-08-11) –
June 26, 1999 (1999-06-26) Nickelodeon (seasons 1-4)
ABC (seasons 5-7) The series premiered on August 11, 1991, as the second Nicktoon after Doug and preceding The Ren & Stimpy Show. 
The series premiered on August 11, 1991, as the second Nicktoon after Doug and preceding The Ren & Stimpy Show. The series premiered on August 11, 1991 on the cable network Nickelodeon, as the channel's first original animated content alongside Rugrats and The Ren & Stimpy Show.