Well, I think that it is much easier to play Maniac Mansion as a separate game. Besides, in English DoTT, poor Ed plays the original unenhanced Maniac of 1988, with worse graphics and only one save slot! It should be easier to find people who played Maniac Mansion inside Day of the Tentacle in Germany or other countries, where Dott had Maniac enhanced inside it.
And today it is even more difficult to play Maniac Mansion inside Day of the Tentacle - it is possible in original hardware & DOS only! ScummVM does not launch it on Ed's computer, and DOSBox allows to launch it - but not to exit it (as you can only shut down DOSBox itself then).