Rugrats - Season 8 - Eps 43: Big Babies
Kevin McNulty, one of Grandpa's old friends (and of course, related to Timmy and the McNulty boys), goes through the secret initiation in order to get into the Loyal Order of Wombats. After seeing this, the Rugrats have Dil go through something similar, so he could become one of the ""Big Babies"". In turn, their fathers mimic the Rugrats, on a bet that they could do everything the Rugrats do.
About Rugrats

Title: Rugrats
First Air Date: 1991-08-11
Last Air Date: 2004-08-01
Status: Ended
Rating: 7.6/10 (from 715 votes)
Language: EN
Seasons: 10
Total Episodes: 322
Network: Nickelodeon
Genres: Family, Animation, Kids, Comedy
Production Companies: Klasky-Csupo, Nickelodeon Productions, Nickelodeon Animation Studio
Synopsis
Focuses on a group of toddlers, most prominently Tommy, Chuckie, Phil, Lil, and Angelica, and their day-to-day lives, usually involving common life experiences that become adventures in the babies' imaginations. Adults in the series are almost always unaware of what the children are up to; however, this only provides more room for the babies to explore and discover their surroundings.
Cast

E. G. Daily
Tommy Pickles (voice)

Kath Soucie
Phil DeVille / Lil DeVille (voice)

Cheryl Chase
Angelica Pickles (voice)

Dionne Quan
Kimi Finster (voice)

Tara Strong
Dil Pickles (voice)

Joe Alaskey
Lou Pickles (voice)

Melanie Chartoff
Didi Pickles (voice)

Tress MacNeille
Charlotte Pickles (voice)

Jack Riley
Stu Pickles (voice)

Cree Summer
Susie Carmichael (voice)