Your question makes no sense with "go in Lois butt", as there is no such episode where 'Stewie goes into Lois' butt', however you may be thinking of Season Four Episode 26 Petergeistwhen the exit of the spirit world was Meg's rear end.
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Season 8 | Episode 13: "Go Stewie Go"
There's no such episode where Lois does it in front of both Meg & Peter.She is however, caught kissing Meg's boyfriend in Go Stewie Go
Lois and clark kiss in the episode "crimson" but Lois is on a drug and clark gets infected w red kryptonite so its not technically real. Also in episode "hydro" but Lois thinks its oliver she is kissing because he is in the green arrow costume. in next weeks episode " crossfire" there are pictures and promos of them kissing as well.Season 8 | Episode 13: "Go Stewie Go"
Season Three|Episode Eleven Emission Impossible
Season 9|Episode 17 Road to the North Pole